Did You Know?

Welcome back to "Did You Know?"!

For the longtime supporters of the Austin Planetarium, we are sure that you remember this monthly column. It is amazing, but Steve Rung, and Torvald Hessel, started this "blog" back in August 2004! Over the years we wrote monthly articles, which quickly turned out to be the most popular part of our website.

However, as the years progressed, we realized the need to update the website as a whole, and also to recreate a new "Astro News" site. With the help of board member Anthony Platsmier, and the design work from NAKA MEdia we upgraded the website, but for Astro News, we simply did not have time, and in March 2010 we wrote the last article.

Needless to say: this has been a thorn in our sides, and we always had in the back of our heads to resuscitate the site, but to add a whole bunch of new stuff! Plus, wouldn't it be great if all those old articles were available again, and better yet: searchable? Well... here you go!

To the right you have the entire index of all the years we wrote these articles. Because there are so many (about 125 articles in total), we split them up in groups of six months. Simply clicking on the links will get you the articles. With the help of volunteers we will be bringing you once again wonderful astronomy and general science content. And... yes the articles are searchable! On the top right of the webpage, there is a little search box. So if you are looking for articles that mention for example "Mars", you get a list of all the appropriate pages returned.

So please join me in saying: Welcome back Did You Know!

NOTE: some of this content is pointing to out-of-date content, and some links may be broken. We will be hopefully fixing those as time progresses.

March 2010

One of the most exciting objects to see through a telescope is undoubtedly Saturn. Of course the familiar Moon will draw gasps when it magically becomes a crater-filled landscape with mountain ranges, ridges and splendid shadows, but Saturn is always a winner. Most people are disappointed when they view Mars, because even when surface features are visible, they're faint and unimpressive. But Saturn, with its splendid rings, is always a crowd pleaser. When they're visible of course...

The rings of Saturn were first observed by Galileo in 1610. He made sketches (see to the right), but Galileo did not understand what he was seeing. He interpreted Saturn as three bodies, maybe other moons or "handles", but the quality of his telescope, and its modest size, severely limited his viewing capabilities. However, two years later, Galileo discovered that what he had observed earlier had changed. To his astonishment the rings had completely disappeared! He wrote "I do not know what to say in a case so surprising, so unlooked for and so novel". So, what happened?

Saturn, just like all the other planets and bodies in our Solar System, rotates around the Sun. Also, in the case of Saturn, its axis is tilted. This is very normal, we have this on Earth, and it's the reason that we have seasons on our planet. The side effect is that we are viewing Saturn from different perspectives all year long; and not just our year, Saturn's year as well. The tilt of the planet Saturn is large enough, that sometimes we are viewing the rings exactly edge-on, making them almost invisible.

The rings of Saturn have incredible dimensions. They are close to a hundred thousand miles wide, but only about a hundred yards thick. As a matter of fact, with the Cassini mission orbiting Saturn we have found that the rings actually extend MUCH farther, like 8 million miles, but are too faint for us to observe from the Earth. The point we want to make here is the enormous difference between the width and the thickness. The rings are so incredibly thin, that when viewed from Earth exactly edge-on, they are pretty much completely invisible; and that is exaclty what happened when Galileo looked at Saturn in 1612.

So how about 400 years later, 2010? Well, last year on September 4th, the rings were exactly edge-on. Right now a little of the rings are visible (about a 4 degree tilt), and at month's end this will have been reduced to 3 degrees, but then we'll be seeing a slow increasing of the tilt. Interestingly, as we move farther away from Saturn, which normally would make the planet appear dimmer, Saturn will actually brighten! The reason is that as we see more and more of the rings, more light will get reflected our way.

February 2010

On the day we write this, the anniversary of the Columbia disaster, there is another sad update to note, namely that the Moon mission that NASA planned, has been pulled. So, at least for the foreseeable future, NASA will not be returning to the Moon. In addition, the Shuttle fleet has only a couple of launches to go and then they will be retired.

That all sounds pretty sad, but potentially this can be a huge break as well. One of the things NASA is eyeing, is the possibility of renting space planes out of the private space industry. If that industry would receive that type of funding, we would be looking at a game changer indeed. One problem though: those conpanies aren't ready yet.

So, I guess, we'll simply wait and see where this all ends. There is a potential of the Shuttle be given an extended life, but that will be expensive and difficult, because the construction of external fuel talks has already been halted and dismantled. Starting that back up would be very expensive.

And the retired shuttles? Well maybe we need to display one right here in Austin. Now THAT would be cool...

Special Event

We have written before about the little-rover-that could, but amazingly, this is still going on. Of course we are referring to the rovers on Mars: Spirit and Opportunity. Originally they were designed to operate for a mere 90 days, but after six years they are still running around on the surface of Mars. So let's have an update.

Spirit
Spirit is still alive, but unfortunately, it is slowly "falling apart" so to speak. Several months ago it came stuck, and despite the best efforts of the NASA engineers, they have been unable to release the Spirit rover. So, now, the rover has been turned officially in a stationary science platform.

Spirit's first task is to attempt to position itself so it will be able to survive the upcoming winter. But, as a science platform, it still will be able to do work, and send the results home to us. In principle the rover can be active like this for many months if not several years. But that is all contingent with repositioning the rover, because in winter, when sunlight is becoming less and at a lower angle, the current position of its solar panels would not generate enough electricity. So, keep your fingers crossed!

Opportunity
Opportunity is in a better condition, and is still driving around. As a matter of fact Opportunity is on its way to a crater called "Conception". This crater is relatively new, with estimates as "young" as only a 1000 years. But when we are speaking in terms of geology, 1000 years is indeed like the blink of an eye.

Opportunity has traveled a whopping 12 miles in the 6 years on Mars, and the 'blog' of Opportunity would be many dozens of pages long if you would print it. You can take a look here on the almost daily updates.

Of course the fact that these two rovers have been at it for so long has not gone unnoticed. Take a look at the following XKCD comic. Enjoy!

January 2010

We have written in the Astro News about the Kepler mission before, and we also blogged about it. The Kepler mission was launched last March and is continually observing 100,000 stars, with one sole purpose: find planets, exo-planets that is.

NASA Kepler spacecraft superposed on Kepler's field of view (image courtesy: NASA/JPL)

Of course you know that we have planets around our Sun, but we have found that other stars have planets as well. These are called "exo planets". But the question that astronomers have been asking over the centuries is: "how prevalent are planets"? Is our Sun special, and more specifically: is an Earth sized planet special or very common?

The problem has always been that stars are so far away, and planets so small, that they are very difficult to observe. Only in the past decade have the telescopes become sensitive enough to observe these, and we have now discovered over 400 planets outside our own solar system! So, one question seems to be answered: planets seem to be common. But until now we have never observed a planet as small as the Earth, but Kepler will change this. Or at least: Kepler can change this.

Kepler will stare for 3 years or more, to this group of 100,000 stars and is sensitive enough to discover planets of the size of the Earth. But, we were convinced that next to that, Kepler would very quickly change our view of planets and our place in the Universe. Because when you have a sensitive instrument, you are bound to find other things as well. And last month, after observing for about 6 months, the Kepler team announced the discovery of its first five planets. What is more, two of these seem to be objects that we do not even know what they are! They are too small to be called stars, but too warm to be a planet. More news to come we are sure!

The Kepler website can be found here. The press release on the discovery of five new planets you can find and here.

Special Event

As mentioned in the calendar section above and previous astro news articles, Mars is in opposition this month, which means Mars is ideally situated for prime viewing! Perhaps you have seen Mars shining brilliantly in the sky. On January 29 Mars is in opposition which means that that Sun, the Earth and Mars are exactly on one line with each other, with the Earth in the middle. At the moment the Sun sets in the west Mars will rise in the east on that day. Before the 29th he will rise a bit later, after the 29th he will rise a little earlier.

For most planets, when the planet is in opposition, this also means that the planet is at its closest approach. But with Mars this is not necessarily the case. The Earth's orbit is rather circular around the Sun, but Mars' orbit is quite elongated. As it happens, Mars will be the closest to Earth on the 27th, and therefore brightest, two days before opposition! However, two years ago, the difference was 6 days, so this opposition is better because Mars appears larger in our sky. We will have to wait till 2013 for a better opposition, so enjoy this one when you can.

Just to give you an idea however how Mars will look like through a telescope we have included the image on the right. This is an animation of Mars, made up from actual images taken through a telescope. You can see how jittery the picture is. That is because the air moves and this causes the image to jump all over the place. If you have a chance this month make sure you try to spot our red neighbor!

December 2009

As you know, besides February a month has either 30 or 31 days. This is no coincidence of course, because our Month is derived from the period of the Moon. Even the name "Month" comes from the word "Moon". The Moon cycle, the period of time from one full Moon to the next, is a little over 29 days: 29.53 to be exact. Another word for this period is the Lunar Month.

So, although the Lunar Month and the regular month are close, they do differ a bit, and this can cause some interesting little facts. If you look for example to this month's calendar you will see that we have a full Moon on December second, but also one on New Year's Eve! Yes, this month has two full moons. This is nothing truly spectacular about this, because every once in a while this happens, about every two and a half years. But, I guess, it was special enough to name this event, and the name is Blue Moon. Every once in a Blue Moon, you get a Blue Moon.

But, there is some confusion on the matter, because some time ago, Sky & Telescope printed an article with a completely different definition, and as it turns out, an improper definition. But taken the fact that this happened back in 1946, everyone had forgotten, until Star Date, the locally produced astronomy radio program, picked it up and broadcasted the wrong definition as well. There is even a wikipedia entry on this:

Sky and Telescope calendrical misinterpretation
The March 1946 Sky and Telescope article "Once in a Blue Moon" by James Hugh Pruett misinterpreted the 1937 Maine Farmer's Almanac. "Seven times in 19 years there were — and still are — 13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, so I interpret it, was called Blue Moon." Widespread adoption of the definition of a "blue moon" as the second full moon in a month followed its use on the popular radio program StarDate on January 31, 1980.

So, do we have a Blue Moon this month? Yess, and I am going to enjoy it, because the next one won't be until 2015.
Happy New Year every one!

Special Event

Wow, what a year 2009 has been for the Austin Planetarium! We raised more money then all other years combined. We went from one employee to three full time and two part-time. We expanded the board by two, and last board meeting installed a board comittee, which has as goal to search and select future board members, because we will be expanding further over the coming year. We also moved offices, from the donated office by NAKA, we moved inbto two offices which are donated by the Center of Space Research of UT Austin. And a new website. And incredible building designs by DAVIS architects. And more advisors, and and...

A lot of this has been happening behind the scenes of course, because not all of them are terribly interesting to our readers, but when I look at the accumulated results, I can say that 2009 waqs a GREAT year for us, even in this economy. But, bigger and better things are to come of course! And this should happen, because we want to build a planetarium and science museum afteral.

So, what are our goals? Well, let me share a wish list with you. One of the things we have been talking about for a long time is to overhaul this astro news page. And yes, that is still on the books, and it will happen for sure in 2010. Additionally, in a week or so of writing this we will turn on our web-store. We fixed all the bugs, and we're ready to create an interesting store for you will all kinds of quality items either related to astronomy, or to the Austin Planetarium. We will also add pages specifically for (science) teachers, and add some Spanish content as well.

But that is the small stuff. The truly *BIG* work is going to be working on securing a location where we will build the Austin Planetarium. Needless to say, when we finally have a "flag in the ground" so to speak, we will be a huge step further. On the same level of achievement would be the announcement of a primary donor, and with that the name of the facility. And I can tell you that things are looking very promising right now.

So, please keep telling other folks in and around Austin about our project, sign up for our news letter, and ask others to do the same. Soon, we will have new bumper stickers that I hope will be seen all around town, because don't you agree it is about time that Austin has a planetarium? We sure think so! Let's make 2010 the year of the Austin Planetarium!

October 2009

As you may have seen from our front page, we are actively rewriting the Austin Planetarium website. (Click image on the right for a larger preview) The current web design is actually 99% the old website of more than a year ago, with the new logo worked in and an updated menu but the content has not changed. The new website will have a much expanded scope in content, and detail much more precisely the Austin Planetarium project. For example, we will be talking in much more detail what kind of Science Museum we're envisioning or what we mean by "Technology Center".

You may wonder if the Astro News will be changing as well. The answer is yes, but not right away. The first focus for the web rewrite is the main content of the site, and we're leaving the Astro News pretty much as it is right now. However, we do have BIG plans for the Astro News. One common complaint is that it is very difficult to find older articles. The Astro News has been written since August 2004, which means we have a total of more than a hundred articles! Another 'problem' is that this page has become rather long to put all in one page. We added the ISS flyover data as well as the Almanac, and things have become rather crowded.

Additionally, there are several more things we want to add to the site. We will add an astronomy dictionary, live pictures of the Sun, links to other astronomy websites like the astronomy picture of the day, etc. So, directly after we go live with the new website, we will begin overhauling your trusted Astro News site. And we love to hear from you! If you have some great ideas of what we should be adding to this site, please feel free to use the form below to contact us.

The new website will be going live sometime in October. We will send out an email to our newsletter subscribers when that happens. You can sign up for our newsletter by using the link at the bottom of any page on this website.

Special Event

The LCROSS, which stands for Lunar CRater Observation and Sensing Satellite, is scheduled to impact at the South Pole of the Moon on October 9th. LCROSS launched on June 18th this year along with the Lunar Reconnaissance Orbiter (LRO) and its mission is to search for water at the lunar poles. You may have heard recently on the news that a new form of water was in fact found on the Moon. It seems to exist as a thin film all over the dust layer that blankets the Moon. LCROSS will be looking mainly to see if water exists in craters that are permanently shadowed.

LCROSS is actually two pieces. The first piece will separate from the second some time before impact. The first piece will stay on its collision course with the Moon, while the second piece changes its trajectory enough to avoid impacting at the same time as the first. After impact NASA scientists expect a large plume of lunar dust to be ejected upward. The second piece will fly through that dust cloud and use instruments on board to determine if water is present in the dust. After it sends its findings back to Earth, the second piece will make its own impact on the Moon, creating another dust plume. Scientists expect to be able to see these dust plumes from Earth and space-based telescopes as well.

Click here to go to the LCROSS mission home page maintained by NASA.
September 2009 As you may have seen from our front page, we are actively rewriting the Austin Planetarium website. (Click image on the right for a larger preview) The current web design is actually 99% the old website of more than a year ago, with the new logo worked in and an updated menu but the content has not changed. The new website will have a much expanded scope in content, and detail much more precisely the Austin Planetarium project. For example, we will be talking in much more detail what kind of Science Museum we're envisioning or what we mean by "Technology Center".

You may wonder if the Astro News will be changing as well. The answer is yes, but not right away. The first focus for the web rewrite is the main content of the site, and we're leaving the Astro News pretty much as it is right now. However, we do have BIG plans for the Astro News. One common complaint is that it is very difficult to find older articles. The Astro News has been written since August 2004, which means we have a total of more than a hundred articles! Another 'problem' is that this page has become rather long to put all in one page. We added the ISS flyover data as well as the Almanac, and things have become rather crowded.

Additionally, there are several things we want to add to the site. We want to add an astronomy dictionary, live pictures of the Sun, links to other astronomy websites like the daily astronomy picture of the day, etc etc. So, directly after we are going live with the new website, we will be starting overhauling your trusted Astro News site. And we love to hear from you! If you have some great ideas of what we should be adding to this site, please feel free to use the form below to contact us.

August 2009

Last month we talked about the new LRO orbiter that is currently circling our Moon, and snapping pictures with greater resolution than ever. Some of the images we were all waiting for, were the images of the Apollo landing sites. The resolution of the camera places the Apollo artifacts easily in range, and perhaps this is a way of convincing some people that we really did visit and walked on our celestial neighbor.

Well, the first pictures are in and they are, without a doubt, quite stunning. Not only can we see artifacts like landers and such, but even tracks in the lunar surface! We have placed some of the images below; please click them to visit the official LRO site to see more.

     

Special Event

You may not have noticed unless you have been paying close attention to the brightness numbers in the table above this article on the International Space Station (ISS). In that case you may have noticed that the ISS has become a lot brighter since we started reporting on the station's visibility for Austin. Another thing you may have noticed is that it looks like that the station is much more often visible then it used to be. well, one is true, and the other we (the authors of this column) are to blame.

Let's start with the brightness of the station. The ISS has indeed become significantly brighter, simply because the station has expanded so much over the years. We started reporting on the ISS sightings in September of 2006. The brightest the station ever became in 2006 was a magnitude of -0.9 on the 17th of November. Remember, magnitude is a little bit of a strange scale, because the smaller the magnitude, the brighter the object. A good analogy is winning first prize in a contest. The first prize is better then second or third, so again, the smaller number the better the achievement. The same holds true for magnitude: the smaller the number, the brighter the object. To put the magnitude for the space station better into perspective, Sirius, the brightest star in the sky, shines at a magnitude of -1.4, and thus was brighter then the ISS in those days, because -1.4 is smaller then -0.9. If we want to express this in brightness, Sirius was about one and a half times as bright, because each step in magnitude is about 2.5 as bright. Two magnitude differences would be 2.5 * 2.5 = 6.25 as bright.

But if we look at the table above, the brightest viewing we have for the ISS this month is a whopping -2.7, and last month the station was shining at -3.3. So since November 2006 the station has become more then seven times as bright! Compared to Sirius, the ISS can be more then five times as bright. Quite a difference indeed!

As stated, this is purely because the station has grown so much. Of course we have been adding modules to the station, but most importantly we installed the full solar panels to generate the power that the station needs, and these solar panels are HUGE. Take a look at the amazing image below. This was taken through a telescope last July, right at the moment when the ISS crossed in front of the face of the Sun. You can see indeed how large the solar panels are, and if you look carefully you can even see the Space Shuttle attached to the station.

Photo by Theirry Legault

Then left to explain is why it looks like that the station seems to be more often visible. As stated, that is completely our doing. We decided that when we started to report on the visibility of the Space Station, to only report the nice and bright ones, because we did not want to disappoint our readers with very poor or short viewings. For this reason we decided to only list the viewings of magnitude zero or brighter. Indeed they used to be pretty rare, but now because the station is so much brighter most viewings meet our criteria. Mystery solved!

July 2009

Even to this day, there are people that firmly believe we never visited the Moon. They claim that the entire Moon landing was faked, and that it was all staged somewhere in a Hollywood studio. This is commonly reffered to as the "Moon Hoax", and I am in the good company of the Bad Astronomer Phil Plait if I state that I am "Skeptical of Denialism"

Now, of course, some people will never be convinced of the truth no matter how much evidence is staring at them. There are still people that believe the Earth is flat, and that the Sun revolves around the Sun and not vice versa! But we do have a great opportunity to settle this issue, and maybe convince a denier or two.

Late last June, a new space craft arrived in orbit around the Moon. This is a mission launced by NASA and its name is LRO, which is short for the Lunar Reconneaissance Orbiter. This craft will do a lot of cool and spectular things (like crashing things into the Moon), but the main thing we want to talk about here is the camera that is on board, specifically the Narrow Angle Camera (NAC). This camera will be able to take very detailed images of the Moon. As a matter of fact the images will be so detailed, objects as small as half a meter (about 18 inches) can be spotted. This means that we should be able to see materials left behind by the Apollo Astronauts! Parts of the landers should easily be visible, as well as several Lunar rovers. And although this month is July, and we celebrate the founding of our nation on the 4th, there is a disappointment. The flag placed on the Moon by the astronauts, is too small to be seen.

For more information on:
  The Moon Hoax
  NASA, LRO Home page

Special Event

Image courtesy NASA

This month marks the 40th anniversary of Buzz Aldrin’s and Neil Armstrong’s historic first steps on the Moon. After a heated space race with the Soviets, America finally achieved the dream to put a man on the Moon. Of course we all know the story by heart, but since Apollo 17, we have not put any more people on our celestial neighbor.

Even though NASA (or any other space agency) has not put any more people on the Lunar surface, we have sent a lot of spacecraft to the Moon for research purposes. With the imminent retirement of the Shuttle fleet, there is talk once again about sending people to the Moon. This time the idea is building a permanent presence.

The idea behind a Lunar base would be that the Moon has a much lower gravity, so it is much easier to launch something from the Moon then it is to launch from Earth. For example, if we want to build a space ship capable of flying people and cargo to Mars, we would save an enormous amount of energy, if we can build and launch this from the Moon.

Maybe in the next decade or two, we will finally reach the times that have been so long predicted in Science Fiction books and movies alike. Maybe one day, when I go on vacation I have the choice between Hawaii, Europe, or the Moon. I know what I would choose!

June 2009

Of course a planetarium is to show the night sky in its most perfect condition. But did you know that these days we can do MUCH more in a planetarium dome? Of course, it is very difficult to prove this to you because we do not have a planetarium, but we will do our best!

The first major revolution that changed the planetarium world was the advent of "full dome video". In the old days we used to have a star projector to project the stars, and then we added slide projectors to add images. At the planetarium in Amsterdam, where I worked for several years, we actually had dozens and dozens of slide projectors all working together, creating an image that covered the entire dome. That was very pretty, but does not even come close to what we can do these days!

Of course you have seen LCD projectors. They are used for presentations in class or any other venue where we need moving video on a large screen. Now imagine taking several much stronger LCD projectors, and somehow "stitch" the separate images together covering the entire dome. That is exactly what we do with full-dome video. The result is a "TV screen" that wraps above and around you. Using video, we can show anything! Not just astronomy - but Biology, Chemistry, or even Architecture!

But, actually, having full dome video really opens up an entirely new experience. For example, when I visited the planetarium in Kiel, Germany I was treated to an amazing music show, created by Jens Fisher. And you bet I did make sure to invite him over to play his show when the Austin Planetarium has been built. The other wonderful thing is I can show you the show right here. The video was shot using a camera in that planetarium (you can see the curvature of the screen), and Jens is sitting at the center creating the music. He is doing this all by himself, live, no recordings, no other musicians, just him. Enjoy!

Special Event

Because Pluto is too far to see with the naked eye, we normally do not talk about this dwarf planet in the AstroNews pages. But this month we are giving some information on Pluto because he is in a special place. Additionally, we talked with a former NASA administrator about Pluto and he had some interesting things to say.

The most detailed color image we have of Pluto, taken in 2001 by the Hubble Space Telescope.

Let's first talk about the Special Event regarding Pluto. Pluto, just like every other object in the solar system, orbits the Sun. The Earth is completing one complete circle roughly every 365 days. Pluto travels a lot slower, and its circle around the Sun is a lot larger. It takes Pluto a whopping 248 years to complete one revolution around the Sun. So, compared to the Earth, Pluto is almost at a standstill! Well, not completely of course; for Pluto to move the distance of the size of the disk of the Moon takes about 4 months! So, more or less, we are passing Pluto each year like he has almost not moved at all.

When we pass Pluto, it simply means that the Sun, the Earth and Pluto are all on one line, with the Earth in the middle. In other words, right when the Sun sets, Pluto will rise and vice versa. This is what astronomers call: Conjunction. Now, please wait! Do not go running out of the door on the night of June 22-23, because you will be disappointed. As we stated before, Pluto is very faint, and you would need a sizable telescope to spot him. Then even if you do have a scope big enough, Pluto is so small and so far away, it will keep looking like a star, and it is very difficult to tell the difference between a star and Pluto. So the trick is to find the proper location, and make a drawing. Then you wait a couple of days and look again and compare the two maps. Pluto will be the "star" that will have moved a little bit. This is certainly a very difficult observational trick!

Now, the NASA administrator story... our Vice President, Lary Cotten, asked him last month whether he believed Pluto was a planet or not, and his answer was: "Get over it! Pluto is a planet! And, yes you can quote me on that." So there you have it, Pluto is still a planet, at least for some people.

May 2009

Due to the work involved to put together this fundraising event, the AstroNews is on break this month, but will return in June.

April 2009

When you fly in space you will be weightless. But do you know the reason? Why are the astronauts in the International Space Station or aboard the Space Shuttle weightless? Most people think this is because that if you travel into space that the gravity of the Earth has disappeared. We have even seen that mistake in school textbooks! But this is very wrong, because the gravity of the Earth goes way further then that! For example, the Moon and the Earth are holding on to each other by gravity. Also, the gravity of the Moon is the cause for the tides on the Earth. If the gravity of the Moon extends all the way to the Earth, the reverse will be true as well. So, if gravity exists in space, how can you be weightless?

The answer to that question is: free fall. Albert Einstein invented a thought experiment to explain. Imagine you are in an elevator. The elevator has no windows, and you do not have any means to communicate to the outside world. If you would be inside the elevator imagine two different situations. A: there is no gravity and you are floating happily inside the elevator, or B: the elevator is in free fall. The interesting thing is, that because you cannot see or hear anything from outside, you will not be able to tell the difference. For you inside the elevator these two situations are 100% the same. In both cases you will be floating inside the elevator.

That is also how the Zero-G flight works. The plane will climb to a great height, and then it will fly downwards, canceling out gravity. You are in free fall. During this time you will be completely weightless and can float around the cabin. Of course you cannot do this for very long, because we don't want to crash. After about 30 seconds, the plane will fly upwards again, and we can repeat the whole sequence. An interesting factoid is that all the weightless scenes in the movie Apollo 13 were shot this way. And now you have a chance to experience this, floating in a weightless environment just as Richard to the left.

The same holds true for both the Space Shuttle and the ISS, and for every satellite that is in Earth's orbit. You are continuously falling down to the Earth, but because you are traveling so fast, the amount you fall is exactly the same as the curvature of the Earth so although, you always fall, you never land. But just as I tell my students: gravity is everywhere! we just can sometimes cheat reality a bit and act like it doesn't exist at all.

Special Event

Have you heard of Yuri's Night? Every year there is a world-wide party taking place on or around April 12th to commemorate the first human being in space: Yuri Gagarin. This year, the Austin Planetarium is celebrating Yuri's night in a *big* way on the evening of April 11th, at the Belmont in downtown Austin.

On April 12, 1961, Yuri became the first human being in space. Of course it was the height of the cold war and the U.S. and Russia were in a very tight race to the Moon. During each phase of the space race, the Russians beat the U.S. each and every time. They launched the first satellite, and then indeed also the first human. He, Yuri, launched on a Vostok 1 (see image on right).

So what do we have planned for you? Well, on the evening of the 11th, we have reserved the upstairs area of the Belmont on 6th street. We will be starting at 7:30 pm with a silent auction and live Russian music with dancers. Then at 8:30, the guest of honor, Richard Garriott, will speak about his space flight to the ISS. This is followed by an update on the planetarium project given by the Executive Director, Torvald Hessel. There will be Russian food available as well as the staple Russian drink: vodka!

The silent auction will include some mission patches from Richard that actually flew with him, a Dell laptop, a Celestron telescope and many more exciting items. The winners of the silent auction will be announced at the same evening around 10:00 pm. Tickets for this event are $25 and are available online.

But there is more! The Grand Prize, donated by Richard, is a Zero-G flight with him! This will be a flight where you will experience weightlessness for about 30 seconds at a time. The plane in question will make parabolic movements up and down, and every time you are going down you will be weightless! Additionally we will be adding the flight from Austin to the event, and two hotel nights as well. On the evening of the 11th we will be starting the raffle for this event. You will be able to buy raffle tickets on our website, or when we have our booth at the Pecan Street festival May 2-3. The raffle will run for about a month, and will close on May 8th, the date of our next event. Raffle tickets will cost $10, and the money will of course support the efforts of the Austin Planetarium to build a planetarium and science & technology center in Austin.

For more information and to keep up to date on this event, please check our Yuri's Night website.

March 2009

Of course, displaying Sun and Moon data on a planetarium page is appropriate, but did you know that a long ago the primary function of astronomers was to tell time? Back in the 17th, 18th and 19th centuries, telling time became more and more important. With the advent of more advanced technology clocks also became better. Even with the most precice clock, you need to know what time to set it to when you first turn it on.

An added problem was that if you travel by ship far to the east or the west, you need to keep track of the longitude to properly tell time. This was also a task for astronomers, who used the stars and the position of the Moon and Sun against background stars to calculate the correct time of the day.

The next problem was how to give this information to the people in the city, and the boats in the harbour. For this the concept of a "Time ball" was invented in 1829. A time ball is a large painted metal or wooden ball that would drop at a specific time, usually 1 pm. This ball would be on a spire on top of the observatory making sure it would be visible from a large area. At about 5 minutes before 1 pm, the ball would be risen and then 2 or 3 minutes before 1, it would be risen all the way. Then at exactly 1 pm, the ball would be dropped. In Sydney Australia (see image below), they also would fire a canon over the harbor at that exact time. If you ever visit Sydney, be sure to witness this, because the ball is still functioning and the canon is still fired every day.

Special Event

Sun and Moon
Sunrise	Sunset
5:29 am	7:35 pm
Moonrise	Moonset
2:36 pm	1:20 am
Current Moon Phase: Waxing Gibbous
Lunar Illumination: 66.82%
Next Full Moon on June 23, 2013, 5:33 am

An almanac, like the famous Farmers' Almanac, is an annual publication with all kinds of data on weather or on the calendar. Astronomical almanacs show data like the rise and set times of the Sun and Moon for a given date. With the advent of computers and the internet, we can now generate data on the fly and display them in a variety of useful formats. So, instead of data for an entire year, often an astronomical almanac shows data for one day. This is exactly what we're showing in the table to the right: The Austin Planetarium Alamanac!

The data displayed is for right now and updates automatically. Of course the Sun and Moon rise and set times do not change during the course of a day, but the illumination changes continuously. That may surprise you, but in 28 days, the Moon goes from New (zero percent illumination), to Full (100%) and back to new again. So in 14 days, we cover 100%, or about 7% per day. Divided by 24 hours in the day, the illumination changes 0.30% each hour! Additionally we are also showing a picture of what the illumination actually looks like, and we're also displaying when the next Lunar event takes place.

Although we have the almanac now properly working, we still want to expand on it, and we also need to find a good permanent place for it in the AstroNews. Additionally, there are several news stations in Austin displaying the same data. The American-Statesman prints it in their paper, courtesy the Morrison Planetarium in California! Now, this information is available from a local source. And better yet, it is accurate for Austin. Data for California is accurate for California

February 2009

This was actually a news article we should have written last month! But in the busy time of years end and all the festivities that comes with it, we simply over looked the fact that last month was the five year anniversary of Mars rover opportunity! On January 24, 2004, Opportunity bounced around on the surface to Mars and came to a stop in a small crater on the Martian surface.

Quite unbelievably, the two rovers (Opportunity joined Spirit which had landed three weeks earlier) are still operational today! After five years, the two ageing rovers are still at it and are still taking pictures and making discoveries. However, after five years, which is twenty times longer then originally planned, the rovers are showing signs of their age. Last month Spirit developed a malfunction and for little while NASA was afraid it would loose the rover, but just like many times before, the rover turns out to be tougher then expected and it looks like Spirit will be fully functional again.

Opportunity has visited four craters, and is on its way to number five, which is by far the largest. This crater is Christened Endeavour and it will still take a while before it arrives. It started its trek towards Endeavour last September, and it may take another 18 months before it finally arrives. But at the current rate, nothing is stopping these two little rovers just quite yet!

Special Event

We have a chance this month to see all five planets in one night! The night in question is from the evening of February 16 to the morning of the 17th. (Actually you would be able to see this a couple of days before and after the 17th)

We start in the evening on the 17th with looking at Venus. Just look to the west just after sunset, and the brightest "star" in the sky is Venus. She will be the easiest to see of all planets. Then about two hours later Saturn rises high enough in the east to be easily spotted as well. Two down, three more to go. But for those three we will have to wait until just before sunrise the following morning.

Look just before sunrise to the eastern sky, on the morning of the 18th the planets will be visible as drawn in the image to the right. And there you have it: all five planets in one night!

January 2009

Our Executive Director, Torvald Hessel, found some meteorites out in west Texas in early December. He was hiking on one of the less frequented paths in Big Bend National Park. In early December, the weather is perfect and the park is nearly deserted. The route offered spectacular scenery that got even more spectacular when he stopped for a rest.

Not a geologist by training, he was still able to recognize a meteorite out amongst all the other native rock. After finding one piece, he decided to look for more. To his amazement, he had found seven sizable fragments within five minutes. Examining the ground further, with renewed interest, he saw dozens more laying around. At that point he realized he had found a site where a meteorite had exploded in the past.

Torvald took the seven meteorite fragments to the park headquarters. The ranger on duty was quite excited by the find. He recounted the facts that indicate there was a large meteorite impact in the area back around 1910. People have been searching for an impact site but haven't yet found it. (Google has part of this account available here). The park ranger showed where they had been searching for a crater, and the site was several miles south of where these fragments were found.

As a matter of fact, a couple of weeks ago another meteorite fall was caught on camera in Canada:



The one in Canada was tiny compared to the one in Big Bend (makes sense, after all everything is bigger in Texas, right?) but seeing this video might give you more of an idea of how overwhelming an event like that is. Normally, as science progresses and we understand better how something works (like lightning), they become less scary.

If you are interested in more details, including how to recognize a meteorite, check out our blog.

Special Event

The Special Event for January is really something that will be special all year long.

2009 is the International Year of Astronomy. The United Nations made this declaration and 135 countries around the world will be participating. This year was selected for several reasons to represent a year to celebrate the past, present and future of Astronomy and all things related. This year is the 400th anniversary of Galileo being the first to point the newly invented telescope up at the sky. In the same year, 1609, Johannes Kepler published his cornerstone work: Astronomia Nova (A New Astronomy). This work contained the first two of Kepler's laws of planetary motion: the first law establishes that planets travel in an elliptical orbit around the Sun. Of course, Kepler was not even thinking about other suns (stars) with planets around them. But 400 years later, we now know for a fact that other suns do have planets in orbit around them.

The Universe, Yours To Discover is their slogan. We couldn't agree more. So many discoveries are still being made in the field of Astronomy today.

We also want to tell you about some of the changes to come during 2009 for the AstroNews. Over the course of the next few months you will see these new features become a part of the AstroNews portion of this website:

• Full Sun/Moon Almanac
  We will have the Sunrise/Sunset times, Moon phase for every night of the month & location. This information will be fully downloadable and we will also make it embeddable in any website.
  
  
• Browsing past articles
  This has been a much requested feature. We will give better access to prior editions of the AstroNews, which goes back over four years now.
  
  
• New Look and Feel
  As you may have noticed, the entire website is transforming its look and feel. We will be engaging more of this in the AstroNews as well as these developments come online.
  
  
• Links to other astronomy resources
  We have always tried to provide links to relevant information in each issue of the AstroNews, but we don't have a comprehensive page for that purpose - soon we will.
  
  
• Live images of the Sun
  We started this last month and it was a hit. Most likely, we will move this information to its own page. For now, it is included still on this page, right here:
  
  
  
  
  
• Additional Educational Materials
  Clearly, we already provide some valuable educational materials for teachers and students alike. In the future, expect to see even more of this content here on this website. Education is what a planetarium is all about. This is still just a sampling of what will be available when Austin has its own planetarium and our doors are open for business.

December 2008

This "did you know" is the last installment of a series of three. In this last installment of this story, we are looking at the connection between sunspots and the Earth's climate.

When Galileo started to use the telescope to look at the sky he made many exciting discoveries. Of course we have heard many of the stories and we have even wrote about several ourselves here in the AstroNews pages. But one that a lot of people do not know is that he also used his instrument to study the Sun, and the things he saw amazed him.

First a warning though: NEVER EVER use binoculars or a telescope to look into the Sun. You will damage your eyes severely and may even become blind. Just looking into the Sun without proper protection is very dangerous. Observing the Sun is dangerous, so make sure you are with a professional that knows what he/she is doing.

Of course, if the Sun did not exist, we would not exist either. The Sun is the source of all our warmth and energy, and without it the oceans would freeze and all life would eventually cease to exist. Another thing we should be thankful for is the constancy of our Sun. We would be in trouble if the Sun became all of the sudden a lot brighter (or dimmer)! However, looking at weather data, there is something very interesting going on. Imagine, for example, sunspots did not exist. What effect would that have on our climate? As a matter of fact between the years of 1645 and 1715, there were almost no sunspots observed. This minimum is called the Maunder Minimum. (see graph below)

During this time, not only did we have record low Sunspot numbers, the climate was also significantly colder! As a matter of fact the period of the Maunder minimum is also referred to as the Little Ice Age. Apparently, if Sunspots are absent for a long time our climate cools down. Conversely, it warms up again when they return. Although we still do not completely understand how this works, the connection seems to be proven.

Now take a look at the following picture of our Sun:

First note the date on the left bottom: that is today's date. This is the latest image taken by the SOHO spacecraft, and this image updates automatically. So, this image is the most recent image of our Sun, and as you can see: there are no Sunspots, and there is little indication that this will change soon. So what is going on?

Last year the Sun went through the normal cycle and we had the Solar Minimum just like every 11 years. But for some reason the cycle has not started back up. On a normal year we should already see some small Sunspot activity, but this time around the Sun is completely devoid of any Sunspots and for over 200 days now this has lasted. This is indeed unusual, but not unheard of. On several occassions there was a time this long without Sunspots but the cycle started up again. And also in this case there is at least some signal that things will return to normal because some were observed in October.

So, pay attention to the image above, and if no more Sunspots occur we may have to get ready for some potential colder weather!

Special Event

The month of December starts of with a spectacular show: Venus, Jupiter and the Moon all coming together in the sky. Venus and Jupiter will be about 4 degrees apart, and then right above it will be the small crescent Moon making the spectacle complete. Sunset will be about 5:30 pm, so set your alarm to step outside at that time and look to the west - you can't miss it! To give you a better idea what to expect (or if you missed it, to show you what you missed) download the animation by clicking on the image to the right. Use your mouse to pan around, and the controls for zooming in and out are at the bottom. You do need quicktime to view it.

Another fun event is on the night of December 10 & 11. The Moon will be one day from full, and will pass over the Pleiades, slowly covering the 7-sisters one by one, only to reappear on the other side some time later. This will starts at around 1:30 in the morning of December 11. No need for directions; just find the (nearly) full Moon and you're all set.

The last thing of note is the Gemenid meteor shower on the evening of the 13th and 14th. Meteor showers are always named for the constellation they appear to emanate from, so in this case it looks like they come from Gemini. One big drawback however is that the Moon will be one day past full and therefore the sky will not be very dark. Only the brightest ones will be visible. But you might get lucky, so lay down a blanket in the back yard and just see if you can spot any shooting stars!

November 2008

This "did you know" is the second of a series of three.

When Galileo started to use the telescope to look at the sky he made many exciting discoveries. Of course we have heard many of the stories and we have even wrote about several ourselves here in the AstroNews pages. But one that a lot of people do not know is that he also used his instrument to study the Sun, and the things he saw amazed him.

First a warning though: NEVER EVER use binoculars or a telescope to look into the Sun. You will damage your eyes severely and may even become blind. Just looking into the Sun without proper protection is very dangerous. Observing the Sun is dangerous, so make sure you are with a professional that knows what he/she is doing.

Last month we talked about the fact that the Sun has spots, which are appropriately called "Sunspots". Although they were discovered centuries ago, it took a long time for us to understand why they exist. What are they? As it turns out, they have something to do with the magnetic field of the Sun. Just like the Earth the Sun has a magnetic field, although in the case of the Sun, the field is much stronger, and a lot more active and dynamic. Take a look for example at the following picture:



This is an image of the Sun taken by NASA's TRACE spacecraft. What you can see is a wildly active solar surface, with matter in big wispy curves over the surface. But if you look closely, you see that these wisps follow lines and loops. What you are seeing are the magnetic field lines of the Sun, the charged particles from the Sun are forced to travel along the field lines resulting in this amazing picture. Additionally you can see at the top left area a very bright region where a lot of the curves seem to emanate from; that is a Sun spot seen from the side! Below we have another image, now from a Sunspot up close.



One of the interesting things with Sunspots is that they are not constant. Sometimes there are many, and sometimes there are (almost) none. After the discovery of Sunspots and people started to track them, we quickly discovered that there was an 11-year cycle of the number of Sunspots. This is also caused by the Sun's magnetic field, because as it turns out, every 11 years it flips around, where north becomes south and vice versa. As it turns out the Sun is an incredibly dynamic and complex place, and we still do not understand everything going on. Something very strange going on with the Sun spots right now, but for that you will have to wait till next month's Astro News.

We'll close this episode with a series of images making a film of the Sun rotating. The bright white spots here are Sunspots, and you can see some incredible solar flares coming off the surface as well. If you look carefully, you can see the bright sunspot on the right producing loops as well and also a flare. (Animation by NASA's Extreme Ultraviolet Imaging Telescope over the course of 6 days, starting June 27 2005. Animation courtesy of SOHO/EIT consortium)

Special Event

There are several great opportunities this month to see the planets and the Moon in conjunction with each other and themselves. You will see them all the better with a set of binoculars. You can see actual craters on the Moon as well as double stars. Those are just a few of the myriad of different things you can see up in the night sky without a telescope. You should have little trouble spotting Jupiter's four Galilean moons; a number of globular clusters will open their doors to you when you put your eyes behind a set of binoculars and point them skyward.

A good set of binoculars is fairly easy to come by and is typically a lot less expensive than a reasonably good telescope. You (or someone you know) might already have a pair stashed away in a drawer or the back corner of a closet. If that's the case, then you won't have to spend an extra penny to get started with looking more closely at the night sky. Just be sure to ask permission to use them if they are not yours.

Binoculars are usually described by two numbers, such as 8x35 or 10x50. The first number is the power of magnification, while the second number is the diameter of the front lens in millimeters (mm). The second number is important for us, because it represents the light-gathering capacity of your binoculars. This translates into how bright objects will appear in your binoculars. For example, a 10x50 pair of binoculars would make things seem 10 times closer. With a little math, we can calculate that our 50 mm front lens has 1963.5 square mm of light-gathering power. How does this compare to your eye? We know that the average diameter of the human pupil in dark conditions is 7 mm, so the light-gathering area for one eye is about 38.5 square mm. That means viewing with binoculars gives your eyes about 50 times more light.

For astro-gazing, you will want to stabilize your binoculars as much as possible, especially for any power above seven. Ones that attach to a tripod work the best, but you can easily brace the binoculars to something stable like a building, car, or a big rock. Go to the darkest patch of sky you can get to on a clear night when the humidity is low and you will be in for a real treat.

Clearly (pun intended), getting started with a pair of binoculars can be fairly inexpensive. The results are instantly rewarding when you take them out on a clear, dark night. Also, this allows you can save your money longer to eventually buy a telescope. The longer you save, the bigger and better the telescope you can afford. In the short-run, you have a set of optics that will get you out at night on a regular basis.

October 2008

This "did you know" is the first of a series of three.

When Galileo started to use the telescope to look at the sky he made many exciting discoveries. Of course we have heard many of the stories and we have even written about several ourselves here in the AstroNews pages. But one that a lot of people do not know is that he also used his instrument to study the Sun, and the things he saw amazed him.

First a warning though: NEVER EVER use binoculars or a telescope to look into the Sun. You will damage your eyes severely and may even become blind. Just looking into the Sun without proper protection is very dangerous. Observing the Sun is dangerous, so make sure you are with a professional that knows what he/she is doing.

Image of a large sunspot group in 2001, as photographed by the NASA SOHO spacecraft.

The thing that Galileo saw was that the Sun was not smooth at all, but that there were dark spots on the surface of the Sun. he even followed the spots for days and determined by their movement that the Sun must be rotating. This was all very disturbing, because Aristotle, the great Greek philosopher, described the Sun as perfect without blemishes. Also the church was very upset because everything God created was perfect, so the sun cannot have spots!

But of course he was right, and the Sun does have spots indeed. What is more, the spots vary from maximums with a lot of sunspots to minimums where we almost have none at all. This all happens on a regular basis called the "Solar Cycle" which lasts 11 years.

Next time we will look closer at this Solar Cycle and also explain more about what sunspots actually are.

Special Event

On October 12th, Austinite Richard Garriott will be taking off for the wildest ride of his life to the International Space Station. The official mission name is Expedition 18. This is not a Space Shuttle mission, but a Russian built Soyuz vehicle and it will be launched from Baikunur in Russia.

Richard (on the far right) with the rest of the crew. For more details see the NASA page

After launch, the Soyuz will chase the International Space Station for two days, and docking will take place on October 14th. Richard will be involved in educational programs through the Challenger Center and also will give interviews while in space. Then after 10 days in space Richard will come back to Earth, and land again in Russia.

Of course we wish Richard all the best at this adventure, and as you can see from the ISS table above, we have some opportunities to spot the ISS right here in Austin!

September 2008

American Astronomer Edwin Hubble (1889-1953)

The Hubble Space Telescope (HST) is named after the famous American astronomer Edwin Hubble (1889-1953). Hubble made several large contributions to the field of astronomy just like HST did so many years later.

His first major discovery was about the size of the universe. For the longest time astronomers thought that the size of the universe was limited to 'just' our galaxy. It was suggested before that the little fuzzies in the sky were actually entire galaxies themselves, but the thought that the universe could be that large was, for many, simply unbelievable. By observing a special type of pulsating star, Edwin Hubble proved that our Milky Way galaxy had many many sisters, and that the universe is incredibly much larger than anyone ever dared to believe.

Today, we know a lot more, but we still do not know exactly how many galaxies there are, simply because there are so incredibly many. No matter where we look into the universe we see millions and millions of galaxies. The current estimate is that there are roughly a hundred billion galaxies, but it can easily be twice that many.

Hubble's second major discovery was equally shocking. It was an accepted fact that the universe was static; the way it looked today was how it looked a million years ago, and how it will look a million years from now. When Einstein developed his theories, one of the things his formulas showed was that the universe was not static, but that it must be expanding or shrinking. He was so appalled by this result that he introduced a new variable to counteract this, because of course it could not be true: the universe was static.

But Edwin Hubble showed that this was not the case at all. By carefully observing galaxies he noticed something interesting: the further the galaxy is situated from our Milky Way, the faster the galaxy was moving away from us! This meant that the universe was expanding and not static at all. The result was what we now call the "Hubble Constant". This constant gives us the relation between the distance of a galaxy from the Milky Way, and the speed it will be traveling away from us. Interestingly enough one of the major scientific results from the Hubble Space Telescope was pinning down this constant more precisely. Previous estimates of the constant had error margins as large as 50%. This error margin now stands at 10%.

Special Event

The Hubble Space Telescope was launched in 1990

For the past eighteen years, the Hubble Space Telescope has been delivering the most stunning images, and has changed the way we view the Universe and the place of our Earth in this universe. Of course the start of the mission was a huge disappointment, after it was discovered that the telescope was unable to focus properly due to an improperly ground mirror. However, after the initial disappointment with some advanced corrective software, science was possible afterall.

The big change came when the Space Shuttle Endeavour visited the telescope in 1993. NASA engineers had created a corrective optics package (called COSTAR) and this was installed in the place of one of the instrumentation packages. The results were stunning, and the story of Hubble after this fix was one of success. After this first servicing mission, the shuttle astronauts visited the telescope three more times: in 1997, 1999 and in 2002. So, it has been six years since the HST was last serviced.

After the Columbia disaster (Feb. 1, 2003) NASA decided that a mission to Hubble would be too risky and cancelled the last servicing mission. The reason it was deemed too dangerous was that if the shuttle would get damaged during the launch like the Columbia did, the astronauts would be stuck in space. With a mission to the ISS this is different because the astronauts would be able to stay at the station until rescue arrives. Unfortunately, the orbit of the Hubble is so trememndously different from the orbit of the ISS, it is not possible for the Shuttle to simply fly from the Hubble to the ISS; there is just not enough fuel.

Because the Hubble Space Telescope is so popular, there was a huge outcry from the general public about this decision, and eventually NASA reverted their decision and scheduled one last mission to the Hubble. To curb the risk, however, they decided that a second Shuttle must be standing by completely ready for launch, in case a rescue mission is necessary. This will be the first time NASA will have two Shuttles ready simultanously.

The launch of this truly final servicing mission, is scheduled for October 8. We hope to bring you news about the mission as it unfolds. One exciting prospect we want to share already is that just like the International Space Station, Hubble is sometimes visible from Austin as well. Next month we will be in luck, because on several nights we should be able to see the Hubble and Shuttle flyover. Stay tuned for more news!

August 2008

A Solar eclipse is a spectacular event, especially when the eclipse is total. If you ever have the chance to witness something like that you should absolutely make time & travel plans because it is an event you will never forget. It is important however to be in the zone of the total eclipse, 99% eclipsed is not good enough, because that 1% of a sliver of a Sun will ruin the experience (although it is better then nothing)

This August 1st, parts of the world will be able to see a total solar eclipse. You can see the path of totality here. Outside the narrow band the eclipse will be partial. But as you can see, the eclipse starts in far northern Canada, goes over Greenland, Nova Zembla, then into Siberia and it ends in China. Unfortunately, for us here in the US we will not see anything at all. :-(

When the solar eclipse is total you can see the solar "corona". Image by Andreas Gada and jerry Lodriguss

We won't go into the reason in this article, but a Solar eclipse is always accompanied by a Lunar eclipse. Lunar eclipses are more common and less spectacular, but anyone who can see the Moon can enjoy the eclipse, you do not need to be at a special place. Well... that is not entirely true: you need to be on the right side of the Earth. Unfortunately, we also will not be able to see anything of that eclipse, because the Moon will be on the other side of the Earth as this spectacle plays out, and by the time the Moon rises for us, the eclipse will be over.

We will have to wait until May 20, 2012 to see an eclipse in the US. But this will be an "annular" eclipse. This means that it happens when the Moon is a bit further away from the earth and is just too small to cover the entire disk of the Sun. So, although fun to see, this is not as spectacular as a total Eclipse. For that we need to wait a little longer: August 21 2017. This will be a spectacular eclipse going from coast to coast. If you want to go ahead and book a hotel in advance, you can see the path here. Hey that's less then 3000 days away!

Special Event

This month's special event is the Perseid Meteor shower. Peak viewing is on the night of August 12th into the morning of the 13th. The Perseids are remnants from the comet Swift-Tuttle and are named for the constellation Perseus. Just like train tracks seem to come together at the horizon, 'shooting stars' of a meteor shower also seem to originate from a single point. In this case, they seem to emanate from the stars that make up the constellation Perseus.

Beautiful example of a Perseid meteor

Meteors are small pieces of rock and dirt varying in size from tiny dust particles to sand grains with an occasional pebble thrown into the mix. When a comet travels through our solar system, the sun heats the comet causing some evaporation. The comet leaves behind a dust trail. When the earth's orbit travels through such a trail, the dust hits our atmosphere at a great speed causing it to burn up. Often, these meteor showers are recurrent and predictable to a certain degree. The Perseid meteor shower is an annual event but the intensity of this year's shower (how many shooting stars per hour) is uncertain. Under a dark sky, 60 - 100 per hour is typical for this shower. However, there are indications this year's Perseids might be a lot better (say 300 an hour). There is always a tiny chance for a spectacular event with 1000's or more per hour, but don't count on it!

The moon cooperates nicely this year for the Perseid Meteor shower. Although the moon is a fat waxing gibeous, it is far to the south and will set early enough to have several hours of good observing before the Sun rises. If the sky is clear and you are away from city lights, conditions should be ideal for observing. The darker the spot you can find the better. Also, make certain you have a clear view of (especially) the North-North Eastern sky. Unfortunately, for most, the best time to observe meteor showers is very early in the morning with the peak around 3 a.m. But with meteor showers things are always uncertain, and you might catch a terrific show before midnight.

Good luck viewing - and if you see a falling star, please wish for a planetarium!

July 2008

It has been speculated for many years, and now we have verifiable evidence that water exists on Mars. This was confirmed by the Phoenix Mars Lander just a couple of weeks ago. Phoenix left Earth last summer and touched down on Mars at the end of May this year. For us to know for certain that water exists on Mars is a huge and relevant piece of news to everyone.

One major focus of Phoenix is to analyze the soil of Mars. We hope to know the contents of the soil surrounding the lander which should give us more insight on the history of Mar's geology. This will also help us determine what humans will need to take on a manned mission to Mars, if and when that happens in the future. The more we understand of what is already there on Mars, the better we are positioned to get there and have a successful mission.

To get soil samples, Phoenix has dug trenches with special tools. Cameras on the Phoenix lander confirmed that white chunks exposed during this trench digging were frozen water. These chunks sublimated over a period of several days. Sublimate means for something to go directly from a solid to a gas form. Because of the atmospheric conditions on Mars, frozen water sublimates into water vapor. There is no liquid water on the surface of Mars.

The images below show a trench dug by Phoenix. They were taken four days apart. Look at the lower left region of both images. There are at least five lumps in the left-hand image that do not appear on the right.

Image credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University

Special Event

On July 1st Mars and Saturn will already only be separated by less than 5 degrees. As an added bonus, Mars will also be just less than a degree and almost directly above the bright star Regulus, which is part of the constellation Leo.

Keep a close eye to this part of the sky from the 1st to the 10th. If you do, you will see the crescent Moon make a short visit on the evenings of the 5th and 6th. During this time you will see Mars move away from Regulus and quite rapidly move toward Saturn.

Mars and Saturn conjunction July 5th and 10th, 2008

By the evening of the 9th, these two planets are separated by less than a degree and remain within two degrees of each other all the way until the 13th.

June 2008

A photon is a "light particle". Well, it is not a particle per se, but it will do for this article. When we look up in the night sky, photons emitted by stars thousands or tens of thousands of years ago will strike your eye and you can see the star. Of course the same goes during the day, but then the photons we mostly see are emitted by our Sun, but the principle is the same.

One thing you will have noticed is that not all stars have the same color. Especially through a telescope this is very visible, some stars are obviously red, while others are yellow or even almost blue. The difference is that the photons have a different energy. Photons with a lower energy are red, and photons that appear blue have a higher energy. But your eye can only see photons within a certain range of energies. If the energy becomes too low, it is called infrared. Infrared is invisible to the eye, but you can feel it because it is "warmth radiation". On the other end, when photons carry too much energy it becomes Ultra Violet, and once again your eye cannot detect this.

But even infrared through Ultra Violet is only a very small potion of energy range that a photon can have. The GLAST mission will be observing photons which are several billions more energetic then the photons that you can see with your eyes. In order to observe these photons you must be in space, because the atmosphere of our Earth shields us from those harmful rays. Take a look at the very informative image below (taken from WikiPedia) with a ton of information about the electro magnetic spectrum, i.e. the energy a photon can have.

May 2008

May will be an exciting month for the further exploration of Mars! On May 25 NASA will attempt to land another spacecraft onto the surface of mars: the Phoenix. Unlike the Mars rovers who landed using inflated airbags to soften the landing, the Phoenix will use a rocket to land on the surface, much like the Viking landers did back in the mid seventies. Landings like this are very risky and difficult, so we're sure that some NASA engineers will be holding their breath during the landing.

Just like the rovers however, the Phoenix mission is planned to last 3 months which may get extended if the mission is successful. Although the Phoenix does not have the ability to move and roam around the landscape like the Mars rovers, the lander does have a long arm to do its research. This arm can dig a hole up to 20 inches deep! Phoenix will land in an area much further to the poles as any of the previous missions (see image below), so we're sure to receive back exciting data and literally out-of-this-world images!

One of the mission goals is to research the possibility of microbial life, specifically whether Mars had ever favorite conditions to harbour life. But of course there is a small chance that the lander would discover something amazing. Be sure to check back to this AstroNews page as the mission progresses, we will keep it updated if anything exciting happens. For more information on this exciting mission please check out the Phoenix home site

April 2008

Four times a year, the Friends of the Austin Planetarium (FOTAP) sends out a free newsletter. This newsletter details our progress bringing a planetarium to Austin, details projects we participate in and also talkes about upcoming events that we are hosting or where we will be present.

If you are interested in astronomy, science education and/or FOTAP's efforts this newsletter is a must. Our latest Winter 2008 newlsterrer is available for download here (opens new window). Please use the form below to sign up for future releases of our newsletter and stay up to date!

Please note: FOTAP will never sell or give away your information to any other group, person or entity without your approval.

UPDATE: signing up for our newsletter can now be done by clicking here.

March 2008

Of course we all have seen the Moon. Probably you have seen our closest neighbor many hundreds of times. But did you know that sometimes the Moon can be of great help finding stars and planets? This month we get an especially wonderful helping hand from the Moon. The Moon is very bright. Of course not as bright as the Sun, but still much brighter then anything else we can see in the sky. So, most of the time the Moon is a distraction, and makes observing more difficult. A star party when there is a full Moon is often considered silly because the "light pollution" from the Moon interferes with observing other sky-wonders.

For this month our show starts on April 4th. This will be just before New Moon, and the Moon will be a very thin sliver. For this showing you will have to look in the Eastern sky just before Sunset and the Moon will be very close to Venus.

A couple of days later, on April 8, the Moon, which will be waxing (=growing) now because we are after New Moon, the Moon will come very close to the Pleiades. This is great, because the Moon is still very dim and its glare will not outshine the Pleiades. If you lived further up north you may even see the Moon covering a couple of the stars of the Pleiades, but here in the deep south we will not see that. But still a very lovely pairing, definitely worth your time. Look to the western sky just after Sunset to catch this show.

Next installment of our Moon-led show is on April 11 where the Moon will pay our red neighbor a visit: Mars. Of course the Moon is not really close to Mars, but it appears this way in our sky. If you look once an hour or so starting at 8 pm, you actually will be able to tell that the Moon is moving through the sky!

On April 14 and 15 the Moon will be pointing out Saturn and the bright star Regulus. And finally our Moon-led star show comes to an end on the early morning of April 27 when the Moon will be just below Jupiter. Have fun catching this month long show!

February 2008

In astronomical diagrams you often see the phrase: "This image is not drawn to Scale". You might wonder why we don't take the time and effort to do draw something to scale? Look for example at the image of the solar and lunar eclipse above. That image is not drawn to scale, but how would it look like if we had drawn it to scale?

Let us assume we will draw the same image to scale, with the Sun drawn the same size as above. Of course the Sun is a lot larger then the Earth, so in the image above we have exaggerated the size of the Earth. The Sun's diameter is 864938 miles, and the Earth is only 7941 miles. So the Sun is more then 100 times as large as the Earth. Taken the fact that the yellow circle is about 50 pixels wide, the earth should be about one half pixel, which is invisible!

But that is not the only problem. If 864938 miles is 50 pixels in the image, then how far should we put the Earth in order to get the proper distance? The Earth is about 91 million miles away from the Sun. If 864938 miles is 50 pixels, then one pixel is 17,298 miles. Then 91 million is more then 5000 pixels. The image above right now is 550 pixels wide, so we need to make it 10 times as wide!

We hope that you now understand that in order to show the Sun and Earth in one picture, we almost always have to draw the image not to scale. Even if we made the image above 10 times as wide, the Earth would still be invisible because it is half a pixel big. Don't we live in an amazing universe?

Special Event

This month's special event is the Lunar Eclipse for February 20. Maybe not as special or as spectacular as a total solar eclipse, this event is definitely worth watching. The other good news is that we do not have to stay up late at all!

A total lunar eclipse takes place when the Moon slides through the shadow of the Earth. (See image below)

So gradually we will see the moon darkening, and on the20th, the Moon will actually almost move through the center of the Earth's shadow. This is not always the case,

Pictures of a total lunar eclipse sequence. Note the reddish color of the moon when totally eclipsed.

because most times the Moon will just graze the Earth's shadow, where one side of the Moon is significantly more eclipsed then the other. A good example is the image to the left: even at mid-totality the lower left is much darker, then the upper right. This time around we will not see such a large variation.

The reason for the red color is also interesting. When the Moon is in the shadow of the Earth, how can we see the moon at all? We can see the moon, even when it is in the center of the shadow, because the earth's atmosphere bends light around its rim. We see the same thing every day: it is already light even before the Sun has risen above the horizon. Somehow the light is bent through the atmosphere. And what color is the sky then? Indeed red! And that is the reason why the Moon appears red.

Unlike a Solar Eclipse, watching a lunar eclipse is completely safe, and does not require any aids like a telescope or binoculars. Just look up and enjoy the show! The moon will start touching the Earth's shadow at 7:05, but the eclipse really starts at 7:43. It will be totally eclipsed from 9:00 pm to 9:52 after which the moon will start slipping out the eclipse again. Have fun observing!

January 2008

The Earth is actually closer to the Sun during our Winter? Strange, but true! Let's look at why.

An elliptical orbit. The small dot in the sun is the actual center of the ellipse.

The Earth's orbit around the Sun is not circular - it is slightly elliptical (somewhat egg-shaped). The Sun is a little bit off of center of this ellipse (it actually lies at one of the two focal points). During January the Earth and the Sun are at their closest to each other. The Sun is actually brighter in the sky during January. This increased brightness goes unnoticed though. Since the Sun is lower in the winter sky, its rays pass through a greater thickness of atmosphere, easily canceling any brightening we might experience.

The earth's axis of rotation is tilted 23.5 degrees from the plane in which it revolves around the sun (see diagram below). Back in December, on the winter solstice, the North Pole reached its greatest tilt away from the Sun. Likewise, on the summer solstice in June, when the Earth is at the opposite side of her orbit, the North Pole will be leaning most directly toward the Sun. Correspondingly, the South Pole is tilted its greatest toward the Sun in December and has its maximum tilt away in June.

So, you might think that the southern hemisphere would endure hotter summers and colder, harsher winters compared with their northern counterparts. The combination of these two effects, being closer to the Sun and being tilted more directly at the Sun, should make for warmer summers and more frigid winters. In fact, the combined effect is not too noticeable. This is due to the large stretches of ocean that cover the southern hemisphere.

A representation of the tilt of the earth's axis in relation to the sun.

However, the current situation has not always been the way of things. These two factors may have combined to produce ice ages in the past. The ellipse that is Earth's orbit gradually rotates around the sun. Like a rubber band being twiddled between two fingers, it completes one total revolution in approximately 23,000 years. This means that over time, the North Pole will eventually be leaning away from the Sun at point in the Earth's orbit when it is furthest away. This could lead to increased glacial activity as in previous ice ages.

For right now, we are at a pretty even balance, so don't go buy a snow blower just yet.

Special Event

Mars is being visited by a number of spacecraft launched from Earth these days. But on January 30th, the Red Planet will be visited by an asteroid. In fact, this asteroid has a small chance of actually hitting Mars. The asteroid, known as asteroid 2007 WD5, actually passed close to Earth in November 2007. It's size is only about 160 feet across, so astronomers have not determined yet whether or not it will strike the surface of Mars.

If it does make a direct hit, it will produce an explosion equal to the detonation of roughly three megatons of TNT. Asteroid 2007 WD5 is travelling at 8.4 miles per second and would leave an impact crater over half a mile across. However, the chances of this asteroid making a direct hit on Mars on the 30th are only 1 in 28, or 3.6% (at the time this article is written). The mobile research vehicle Opportunity will be close, if an impact actually occurs. But, the Mars rover will be safely to the south of the potential target region.

Please visit the home page of the Near Earth Object Program to get updated details on the possible impact of 2007 WD5 on Mars.

An extra-terrestrial impact has happened in the not-too-distant past. In July 1994 Comet Shoemaker-Levy 9 actually impacted Jupiter. The comet had been torn apart by Jupiter's gravity, and 21 fragments of the comet succumbed to the giant planet.

Comet Shoemaker-Levy 9 and Jupiter image courtesy NASA

December 2007

Have you heard? It is going to rain! Well, to be more exact, we will get a meteor shower with the best chance to see falling stars on the 14th. This meteor shower is an annual repeating event and is called the Geminid Meteor Shower.

As for all meteor showers, all the shooting stars seem to originate from the same piece of sky, and that gives the shower the name. In this case the stars look like to emanate from the constellation of Gemini. Although we'll miss the very peak of activity we still have a great chance to spot some shooting stars. The best chance we have around 9-10 pm on Thursday December 13th. There should be still some additional activity on the following night, but probably less then the 13th. During the peak about 140 meteors per hour are predicted, on the 13th we should be able to see one a minute at least.

Observing meteors is very easy. Just bundle up and lay down in your lawn. The darker the better of course, and you should have an unobstructed view of the sky, but that is all that it takes. If you are with more then one, try each looking at different sections of the sky. But you do not need any telescopes or binoculars for this type of observing. Shoot us an email when you are successful observing this meteor shower!

Special Event

As you undoubtedly have heard in the news or on this very Astro-News page: Mars is spectacular! Perhaps you have seen him already shining brilliantly in the sky. On December 24 Mars will be in opposition which means that that Sun, the Earth and Mars are exactly on one line with each other, with the Earth in the middle. At the moment the Sun sets in the west Mars will rise in the east on that day. Before the 24th he will rise a bit later, after the 24th he will rise a little earlier.

For most planets, when the planet is in opposition, this also means that the planet is at its closest approach. But with Mars this is not necessarily the case. The Earth's orbit is rather circular around the Sun, but Mars' orbit is quite elongated. As it happens, Mars will be the closest to Earth on the 18th, and therefore brightest, six days before opposition! An unfortunate side effect of this, is that this years opposition is a rather poor one. Although Mars is bright and close by, the last 3 oppositions were much more favorable.

Just to give you an idea however how Mars will look like through a telescope we have included the image on the right. This is an animation of Mars, made up from actual images taken through a telescope. You can see how jittery the picture is. That is because the air moves and this causes the image to jump all over the place. If you have a chance this month make sure you try to spot our red neighbor!

November 2007

Mars will start showing *retrograde* motion in the sky on November 15th and will continue doing so until January 30th, 2008. What exactly does that mean? Well, let's start with what does the word *retrograde* mean? It comes from two Latin words: gradus (meaning "step") and retro (meaning "backwards"). Mars will literally appear to stop its eastward movement across the sky in relation to the stars on the 15th. Then, over the next 10 weeks, Mars will first make a gradual loop and then move westward, before looping back to its eastward motion.

2005 Mars Retrograde image courtesy NASA

Interestingly enough, the retrograde movement of planets (because Jupiter and Saturn show similar movements) was the main reason for Copernicus to doubt that the Earth was at the center of the universe and that everything moved around the earth. There were many very strange explanations of this movement, but Copernicus was the first one to truly explain what was really going on. By putting the Sun in the center, and having the planets move around the Sun, this retrograde motion became not only explainable, but also predictable.

Special Event

A Comet Visible to the Naked Eye

This special event actually started back on October 24th, but continues to be an item of much discussion in the astronomy world. A comet known as Comet Holmes brightened in a dramatic fashion on that date. It went from magnitude 17 (which is not visible to the unaided eye) to magnitude 2.5 (which is easily visible to the unaided eye). It did this practically overnight, increasing its brightness by almost a factor of a million.

Prior to last week, Comet Holmes probably was not known, except to astronomy folks. Now he has exploded into the scene as an object so bright in the night sky that only the Moon, some of the planets, and a small number of stars are brighter than it. This is quite amazing and certainly not a common occurrence in the night sky. Our ancestors looked to the sky as a place of unchanging beauty and took careful note if something all-of-a-sudden showed up there. They might have made some world changing prophecies based on the arrival of such a bright comet. We will not make such bold predictions, except to say that maybe we can take this as a sign that a planetarium is in the future for the city of Austin and its surrounding communities.

Comet Holmes in Perseus image courtesy Sky & Telescope

Located just on the edge of the constellation Perseus, Comet Holmes should be fairly easy to locate. Look to the Northeast at about 8:30 p.m. (7:30 p.m. after we go off of Daylight Savings Time). Almost straight down from the brightest star in Perseus, Mirfak or Alpha Persei, you should see Comet Holmes. The distance between Mirfak and Comet Holmes is about the width of your thumb held at arm's length. Since Sky & Telescope already has an excellent website for observing this comet, we are linking to that site here. They are making daily updates to it and feature many pictures of the comet, descriptions of observations, and much more detailed instructions for locating it.

October 2007

Have you heard the news? Someone from Austin is going to pay the International Space Station a visit in 2008! As of today, five space tourists have visited the ISS, each spending about $25 million. Because NASA is not allowed to take up tourists, all these flights have been carried out by the Russians.

The first ‘fee paying’ space tourist was the American Dennis Tito in 2001. After Dennis, the South African Mark Shuttleworth was the second in 2002, followed by Gregory Olson (US) in 2005, Anousheh Ansari in 2006 and finally Charles Simonyi earlier this year.

The lucky Austinite, and the sixth space tourist, is Richard Garriott. Richard is the son of astronaut Owen Garriott, who spent 60 days aboard Skylab in 1973, and 10 days aboard Spacelab-1 in 1983. So interest in spaceflight is nothing new to Richard. His flight is scheduled for October 2008.

We wish Richard all the luck and we are intensely proud that someone from Austin will fly to space. Of course we will be sending Richard a “Friends of the Austin Planetarium” T-shirt to wear when he is visiting the ISS.

Special Event

This month the Space Shuttle is once again blasting off to visit the International Space Station (ISS). Taken the fact of the wonderful viewing opportunities we have this month, we will dedicate this month’s ‘Special Events’ to the ISS.

Originally, the US had planned to build a space station independently (i.e. without using any international partners) called Space Station Freedom. However, due to funding cuts, this project could not be completed as envisioned. At the same time Russia was planning a MIR 2 and had similar financial woes. Soon a plan was hatched to combine efforts. The current ISS is a merger between Space Station Freedom, MIR 2, the European Columbus module, and the Japanese Kibo modules. The latter two still need to be launched.

The current mission, which is the twenty third mission to the ISS, will deliver and install the Italian build ‘Harmony’ module to the ISS. This module is the connecting module between the ISS and the Columbus and Kibo modules. (see images below) When this module is installed, the ISS is indeed ready to receive the other two. Columbus is scheduled to be launched December 6, 2007. The Kibo modules will be launched in 2008 on February 14 and April 24. Of course these dates are not 100% certain and might be readjusted by NASA.

The International Space Station is currently the largest structure ever constructed in space, and has been continuously inhabited since November 2, 2000. It orbits the Earth at an altitude of 319 km to 346 km (197.5 – 216 mi) and travels at a speed of 27,744 km (17,240 mi) per hour, or almost 16 times around the Earth each day.

As stated in the calendar section, we have 5 opportunities to spot the ISS in a row; October 22 through 26. Potentially the most spectacular one is on October 23 right after the launch of the Space Shuttle. It takes some time for the Space Shuttle to catch up with the space station, so we should be able to see two bright dots traveling through the sky. We’ll keep you updated on any launch update. Have fun spotting the ISS this month!

September 2007

In 1610, Galileo was the first person to use a telescope to observe the planets. One of the planets he observed was Saturn. Saturn was the farthest planet known at that time. Uranus and Neptune had not been discovered yet. The telescope he used he had build himself and was able to magnify about 20 times. What Galileo observed puzzled him, because Saturn looked 'weird'.

He made several sketches (see compilation on the right) but it is obvious from those sketches that he did not understand what he was seeing. He thought the rings were "handles" or large moons, one on each side of the planet. He stated: "I have observed the highest planet [Saturn] to be tripled-bodied. This is to say that to my very great amazement Saturn was seen to me to be not a single star, but three together, which almost touch each other"

But the mystery for Galileo deepened further when he again looked at Saturn two years later in 1612: the rings (or moons as he thought) had disappeared! What was clearly visible in his telescope only two years earlier, had completely vanished. Again in Galileo's own words: "I do not know what to say in a case so surprising, so unlooked for and so novel". So what had happened?

Just like the Earth, Saturn orbits the Sun under an incline. The Earth's incline causes our seasons, but observed from another planet the Earth will look like to 'wobble'. Sometimes it leans to the right, and then again to the left. The exact same is true for Saturn. However, because Saturn has rings, the effect is quite more spectacular, as is visible in the Hubble Heritage image to the left.

In this image there are 5 pictures taken by the Hubble Space Telescope of Saturn, at different times. The top image shows the rings most clearly, and the bottom they're almost gone, making the planet a lot dimmer of course. But right at the point where we are seeing the rings 'edge on' they seem to disappear completely. The reason is that the rings are very wide (about 175,000 miles) but comparatively incredibly thin: only 3200 feet! Because the rings are so thin, they are as good as invisible when they are edge on.

Right now, the rings of Saturn are indeed becoming 'smaller' as seen from the Earth, but for them to 'disappear' again, just like what Galileo observed; we will have to be patient, that won't happen until the fourth of September 2009. Plus we are not in luck then, because at that point, Saturn will be too close to the Sun for us to observe well. The next occasion, 23rd of March 2025, we don't fare much better. No, we'll have to wait until 2038-2039 to get a good showing!

Special Event

Taken the fact that this month there are no astronomical events of great importance, and we already discussed the Dawn mission in the July edition of Astro News, we will be talking about an upcoming event: the opposition of Mars. Recently we received several emails asking about Mars, and why Mars is getting brighter and dimmer.

Both Mars and the Earth are in orbit around the Sun, as depicted in the top image on the right (drawings not to scale). In the images, the Sun is in the center, the Earth is the blue dot, and Mars the red dot. And the arrow indicates in what direction the planets are rotating around the Sun. Of course, you already knew Mars is further from the Sun than the Earth; that is one reason why it is so cold on Mars.

But because we are so much closer to the Sun, the Earth experiences more gravitational pull from the Sun, so the Earth will move faster than Mars, which experiences less pull. On top of that, because the orbit of Mars is so much larger, it takes Mars a lot longer to complete one circle (one Mars year) around the Sun. The Earth takes 365 days, while Mars takes almost twice as much: 668 days.

The result is that every so often, the Earth catches up with Mars. Right now, the situation is approximately as depicted in the top image. We're behind Mars, and that is why Mars rises late in the evening. But as we catch up, and start to move towards the lower image, Mars will rise earlier and earlier. When Mars is directly opposite the Sun, Mars will rise at the exact time the Sun is setting. From that time on, Mars will move away from the Earth again. Now if we would tell you that the orbits of Mars and the Earth are actually ellipses and not circles, we'll make your head spin, so we will talk about that another time.

This happens about every 2.5 years, Mars' opposition will take place around Christmas this year, and we'll be sure to pay more attention to this exciting event! In the mean time, see if you can spot Mars before Sunrise this month!Taken the fact that this month there are no astronomical events of great importance, and we already discussed the Dawn mission in the July edition of Astro News, we will be talking about an upcoming event: the opposition of Mars. Recently we received several emails asking about Mars, and why Mars is getting brighter and dimmer.

Both Mars and the Earth are in orbit around the Sun, as depicted in the top image on the right (drawings not to scale). In the images, the Sun is in the center, the Earth is the blue dot, and Mars the red dot. And the arrow indicates in what direction the planets are rotating around the Sun. Of course, you already knew Mars is further from the Sun than the Earth; that is one reason why it is so cold on Mars.

But because we are so much closer to the Sun, the Earth experiences more gravitational pull from the Sun, so the Earth will move faster than Mars, which experiences less pull. On top of that, because the orbit of Mars is so much larger, it takes Mars a lot longer to complete one circle (one Mars year) around the Sun. The Earth takes 365 days, while Mars takes almost twice as much: 668 days.

The result is that every so often, the Earth catches up with Mars. Right now, the situation is approximately as depicted in the top image. We're behind Mars, and that is why Mars rises late in the evening. But as we catch up, and start to move towards the lower image, Mars will rise earlier and earlier. When Mars is directly opposite the Sun, Mars will rise at the exact time the Sun is setting. From that time on, Mars will move away from the Earth again. Now if we would tell you that the orbits of Mars and the Earth are actually ellipses and not circles, we'll make your head spin, so we will talk about that another time.

This happens about every 2.5 years, Mars' opposition will take place around Christmas this year, and we'll be sure to pay more attention to this exciting event! In the mean time, see if you can spot Mars before Sunrise this month!

August 2007

In mythology the phoenix is a bird with beautiful gold and red plumage. At the end of its life-cycle the phoenix builds itself

Phoenix detail from Aberdeen Bestiary

a nest of cinnamon twigs that it then ignites; both nest and bird burn fiercely and are reduced to ashes, from which a new, young phoenix arises. (Source: Wikipedia.org)

However, the launch of the Phoenix this month to Mars is a different kind of 'beast'. The orbits of Mars and the Earth are such that every two years (actually every 25 months) the two planets pass each other on the same side of the Sun. About five months before the two planets are on closest approach is the ideal time to launch spacecraft to Mars. The same way the two Mars rovers, Spirit and Opportunity, were launched two years ago, as was the Mars Reconnaissance Orbiter. This time NASA will be launching another lander: the Phoenix.

The Phoenix lander will cruise for about 9 months and then, if everything goes right, perform a controlled landing near the North Pole. First, it will deploy a parachute, and then when it has sufficiently slowed down, it will fire its retro rockets and land on its landing legs. This will be the first soft landing on Mars in thirty years! The last time this was done successfully was in 1976 by the two Viking landers. Unfortunately, less then 50% of the spacecraft attempting to land on Mars have been successful, and the last soft landing attempt by the Mars Polar Lander ended in failure.

This brings us finaly to the name of the mission: Phoenix. The Phoenix mission carries some of the instruments derived from the failed Mars Polar Lander mission. So in a sense, this mission is indeed the rebirth of a previous mission. Let's hope Phoenix will be successful this time and not end in a fiery death. When Phoenix get closer to Mars we will talk again about this mission in the Astro News, and give some more detail about what the mission of the Phoenix entails.

July 2007

Astronomers of all kinds like to throw a party. This party doesn't involve bright lights or a bunch of noise. This party requires some telescopes (the more, the merrier), a group of people who appreciate the stars and planets and a nice, quiet dark sky (the darker, the better).

This kind of party is called a Star Party. People from all walks of life and all ages are welcome at this party. People who know just a little or nothing about astronomy are very welcome here. People who know a lot about astronomy are at the Star Party and are very willing to share the eyepiece of their telescopes and teach others about the fun and science of astronomy.

The Austin Astronomical Society and St. Stephen’s Episcopal School is throwing just such a party during the month of July. Please mark your calendar for July 21, a Saturday, for "Austin Under the Stars" at St. Stephen's School.

Normally The Friends of the Austin Planetarium will be there with our StarBubble, but this it looks like both gym's are under construction. So we will probably not be able to offer free planetarium shows this year. However we do have a wonderful "magic Globe" from Global imaginations to show. So even if we do not have a planetarium show for you to show, we do have this amazing globe!

We will also have mugs available. Come by and find out how you can get one! We'll be glad to talk to you about what you can do to help bring a planetarium to Austin.

The event runs from 6:00 p.m. until midnight. Solar viewing and the Magic Globe begin at 6:00 p.m. with the star party kicking into gear at about 8:00 p.m.

See ya there!

Special Event

NASA is set to launch the Dawn spacecraft this month on a long and winding road to the giant asteroids Vesta and Ceres. Currently, Delta is set to launch July 7 from Cape Canaveral atop a Delta II rocket.

Once launched, Dawn first will head for Mars. After a journey almost two years, Dawn will fly within about 300 miles of the Red Planet in April 2009. While Dawn may test out its science instruments on Mars, the real benefits of this planetary swing-by are navigational. First, it will give Dawn a boost in speed of about 7,000 miles per hour (relative to the Sun). Second, the maneuver has been choreographed to send Dawn up and out of the plane of the solar system – because that is where its first main target, the asteroid Vesta, lives.

Dawn should arrive at Vesta in 2011, and study it for a year. It will then set out for the largest of the asteroids – or, depending on your point of view, the smallest of the planets -- Ceres. Dawn will take three years to reach Ceres, getting there in 2015.

Dawn will measure the detailed shape, size, and mass of Vesta and Ceres, the composition of their surfaces, the structure of their interiors, what role water played in their evolution. These studies will help us understand how the terrestrial planets in our present-day solar system formed.

For more information, check out Dawn’s website at http://dawn.jpl.nasa.gov/. Next month we will talk about the Phoenix mission, which unlike the Dawn mission will actually land on Mars.

June 2007

Although we will not talk about the Dawn mission in this issue of AstroNews, we will talk about the name: Dawn. The meaning of dawn that you are probably familiar with is something like "Just before sunrise when the horizon starts to lighten". It may surprise you but an exact definition of dawn exists. Not only that, but more than one type of dawn is defined.

The three different dawn definitions have different names. You have "Civil dawn", "Nautical dawn", and "Astronomical dawn". The one thing they all have in common is that the Sun is still below the horizon, but they differ in the definition of how much. Here is the full definition of each:

• Astronomical dawn is the time at which the sun is 18 degrees below the horizon in the morning. Astronomical dawn is that point in time at which the sun starts lightening the sky. Prior to this time, the sky is completely dark.
  
  
• Nautical dawn is the time at which the sun is 12 degrees below the horizon in the morning. Nautical dawn is defined as that time at which there is just enough sunlight for objects to be distinguishable.
  
  
• Civil dawn is the time at which the sun is 6 degrees below the horizon in the morning. Civil dawn is defined as that time at which there is enough light for objects to be distinguishable and that outdoor activities can commence.
  
  

Special Event

Currently the two Mars rovers, Spirit and Opportunity, are still roving around the planet and are alive and well. Of course things are slowly breaking down because they were not designed to operate this long. But NASA is doing everything to stretch the missions because the rovers are still returning amazing data.

Next to the rovers, the Mars Reconnaissance Orbiter is also producing also amazing results. The highest resolution images come from this mission and we are seeing the red planet in more detail than ever. But there are still more missions. Mars Express and Mars Odyssey are two other missions that are currently operational, but that's not all. On June 30th we will see the launch of yet another mission to Mars. This mission is called "Dawn", and in August NASA will launch the "Phoenix" mission. It's going to busy around our red neighbor! Next month we will explain about these two missions in more detail, so stay tuned!

May 2007

Each planet in our solar system goes around the Sun in a different amount of time than the Earth. Of course a year is the time it takes for a planet to go all the way around the Sun once. So, each planet's year is shorter or longer than that of the Earth. The Earth takes about 365.25 days to go around the Sun once. (Note: we will just talk about Earth days here. Each planet also has its own length of day, so things could get a bit confusing if we try to take on too much at once.) The planets closer to the Sun have a shorter year than the Earth, while the ones further from the Sun have a longer year.

Here is a chart showing (in Earth years) how long it takes each planet to go all the way around the Sun once:

Consider this: you would be a different age on the other planets. I have a friend who recently turned 40. That's 40 in Earth years. She would already be 65 in years on Venus, but still just 21 years old on Mars - and less than 4 years old on Jupiter. So, take your pick: retired, in college, or still a pre-schooler with these extra-terrestrial ages. Using the chart above and the following formula, you can easily calculate your own age in each planet's years:

X = Your current age
Y = Any number from the chart above

X / Y = Your age in another planet's years

Are you an old wo/man on Mercury? Still an infant on Saturn?

April 2007

As you know, our Sun has a yellow color, but a lot of other stars (which are suns as well) have completely different colors. Betelgeuse for example, in the constellation Orion, is red. In the same constellation however, there are several stars that are much bluer then our Sun. Look at the image below, and notice the different colors of stars. How come the difference?

Constellation of Orion

The cause of these color differences is temperature. Every star is different, just like every human being is different, and different stars have different temperatures. Maybe surprisingly a red star is a lot cooler then a blue or white star. But we can understand it with the following example. If you take a piece of iron and hold it in a flame, it will become red-hot. It indeed will start to glow red. But when we make it even hotter, it will become a lighter color, more towards yellow. After yellow it will become white-hot.

The same principle holds true for stars. Our Sun has a surface temperature of about 6000 Kelvin (10,340 F) but Betelgeuse has a surface temperature of 3650 Kelvin (6110 F). Rigel however, another star in the constellation of Orion, has a surface degree of 11,000 Kelvin, that is almost twenty thousand degrees Fahrenheit!

Special Event

As you can see from the calendar this month, there is not much spectacular going on in the sky this month. Even the Space Shuttle launch that was scheduled for early April has been postponed to a later date, because the external fuel tank was damaged by hail last month. The Space Shuttle will most likely launch somewhere early next month.

But thankfully, there is CenTex! Centex astronomy weekend is an event organized by our friends from the Austin Astronomical Society (AAS). This annual starparty is held at the Canyons of the Eagles state park on Lake Buchanan. AAS has a nice observatory there, and during this weekend the observation field is open to the public. You will have the chance to look through dozens of telescopes. Additionally, there will be lectures about astronomy.

Centex is held on April 20-21, and is free and open to the public. For more information and driving directions, please check www.austinastro.org/centex.html.

March 2007

Last month we talked about the fact that gravity exists everywhere. But if this is true, how can an astronaut float in space like there is no gravity at all? Obviously something is different up there! Well, not exactly. It is not about where the astronauts are, but more about how they are moving relative to Earth. If the circumstances are right, you can be weightless right here on Earth!

In both cases you experience 1G gravity in the elevator

Einstein came up with a good explanation, and it is still used today to explain his theory of general relativity to students. It is the famous “elevator” example. Imagine you are in an elevator (see illustration on the left). The doors of the elevator are closed, and there are no windows in the elevator. In case A, the elevator is on Earth, and does not move. You would experience a gravity of one G, just as you would expect.

But elevator B is in deep space, in an area where there is no gravity (although we know this does not exist, for this example we imagine that it does). This elevator is accelerating because we strapped a (completely silent) engine to it. The acceleration is equal to one G. The interesting fact is, a passenger inside elevator A or B would be unable to tell the difference between the two — the motionless elevator on Earth and the moving elevator in space would feel exactly the same to the people inside them.

In both cases you experience no gravity in the elevator

This is exactly what happens with the astronauts. They aren’t really in an area without gravity — they are in constant free fall around Earth! Therefore they experience a zero-G environment. NASA even operates planes that simulate zero-G. The plane flies in an up, down, up pattern over and over. Every time the plane dives down, passengers are weightless for about 25 seconds, and that is not even in space!

Special Event

The first special event of the month is the lunar eclipse of March third. Although not as spectacular as a solar eclipse, this event is still something to pay attention to. In this case, we will not be able to see the start of the eclipse, because at the time the Moon rises, it will already be in full eclipse. This probably will make things even more spectacular, because now the Moon will be dramatically red when it rises. Another benefit of a lunar eclipse over a solar eclipse is that it is completely safe to watch. The Moon will not blind you as the Sun does. Also the time is perfect for observation, because when the Moon is full, it rises at the exact same time the Sun sets. For Saturday this will be at 6:31 pm.

The second special Event of March is the vernal equinox. The vernal equinox is March 20 this year, at precisely 7:07 p.m. CDT. The word “equinox” is Latin for equal night. That means that on the equinoxes, both spring and fall, the length of night and day are equal. But do you know why?

A representation of the ecliptic and the apparent path of the sun

The solstices are also related to the ecliptic. The summer solstice marks the date that the Sun appears highest in sky at noon, and this day has the longest amount of daylight for the year. The winter solstice is when the Sun appears lowest in the sky at noon, and has the least amount of daylight for the year. These are the Sun’s high and low points on the ecliptic.

February 2007

Astronaut in zero-G? Image courtesy: NASA

When you see pictures of astronauts floating in space, we are talking about a zero-G environment. But it is a mistake to think that there is no gravity up where the Space Shuttle floats. Unfortunately, this misconception is widespread; we even have found it in schoolbooks.

Gravity is everywhere. Of course we know gravity from our daily lives, walking on the surface of the earth. But the pull of our planet goes much further than that. Ever wondered why the Moon does not just 'floats away'? Exactly: the Moon and the Earth are gravitationally bound. Not only does the gravity of the Earth reach the Moon, the reverse is true as well. Actually you know this, because the ocean’s tides are a direct result of the pull from the Moon. And there's more. As the Earth revolves around the Sun, the gravity of the Sun also has an affect on the tides. Without the Sun we would not have spring-tides, for example.

So how far do you have to travel to have no gravity? Well, Pluto is also connected by gravity to the Sun, so that's not far enough. Did you know that the Sun revolves around the center of our galaxy, the Milky Way? Indeed, the Sun (actually the whole Solar System) is gravitationally bound to the Milky Way. Going urther out, gravity still exists, and plays a major role. The Milky Way and Andromeda Galaxies are on a collision course, all because of the gravitational pull between the two! Don't worry though - this collision will not take place for another three billion years.

So, galaxies revolve and interact with each other because of gravity. On even the largest scales in the universe, whole galaxy clusters work together combining their gravity. Gravity is everywhere.

Now, you might ask, if gravity is everywhere how is it possible for astronauts to float? Shouldn't they fall? Well, stay tuned, because that will be the subject of next month's AstroNews.

Special Event

New Horizons Flyby of Jupiter

At the end of this month, the New Horizons spacecraft, whose destination is Pluto, will fly past Jupiter on its way to the outer reaches of the Solar System. Launched by NASA on January 19, 2006, New Horizons is currently traveling at 43,000 miles per hour. After the Jupiter flyby, using its gravity to slingshot off toward Pluto, it will be traveling at around 52,000 miles per hour.

Artist's Impression of New Horizons spacecraft Jupiter flyby Image courtesy: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

This puts New Horizons at Jupiter in just over 13 months. Let’s put that in perspective with how humans usual travel. If New Horizons were going at the speed of a car on the highway, so around 70 miles per hour, it would take over 673 years for it to reach Jupiter at that speed. 13 months is the quickest of any man-made spacecraft to reach the giant planet.

New Horizons will test most of its onboard equipment during the flyby. Even though it will be 1.4 million miles from Jupiter, it will be close enough to study the planet and its moons in detail. New Horizons is designed to gather months of data before transmitting it back to Earth. It will conduct tests similar to its Pluto encounter while visiting Jupiter, so that any necessary adjustments can be made now.

After reaching Pluto in July 2015, it will spend five months studying the dwarf planet and its three moons. It will study the geology, structure and atmospheric conditions of those bodies. If all goes well, it will then conduct similar studies on smaller objects in the Kuiper Belt, the region far beyond Neptune’s orbit populated with rocky, icy objects.

Visit the New Horizons website for many more fun details about this mission, and even track where the spacecraft currently is at.

January 2007

Have you ever wondered how far can you see? Of course, you can see buildings or mountains in the distance, but when you look up in the sky you realize that you can see a lot further then you probably thought. The closest star other then the Sun, Proxima Centauri, is about four light years away. Wow, that's about 23,498,359,696,815 or more than 23 trillion miles away.

But of course all other stars are further away then that, because Proxima Centauri is the closest star. The farthest star visible with the naked eye is in the Southern hemisphere and is called 's Carinae'. This star is so bright, we can see it from a distance of more then 11 thousand light years, or more then 64 quadrillion miles.

M31, the Andromeda Galaxy Image courtesey NASA

Special Event

Happy 2007!

So, what can we expect in 2007? If you have been a regular reader of the Astro News pages, you will understand that every month there is something interesting happening in the sky. But a couple of events do stand out for 2007.

Composite Image of a Lunar Eclipse Image courtesey epod.usra.edu

There is also good news for planetary observers: Mars, Jupiter and Saturn will all reach opposition in 2007, and will be perfect to observe. Saturn will be the first in February, then Jupiter in June and Mars in December. Of course we will write in detail about these events, so stay tuned.

But of course there is much more to look forward to. There will be the regular meteor showers, Shuttle launches, and chances to see the International Space Station. And who knows... maybe even some announcements of astronomical size about a planetarium for Austin!

December 2006

Farewell Mars Global Surveyor

Ten years ago, on November 7 1996, a new mission to the planet Mars was launched: the Mars Global Surveyor (MGS). Hopes were very high for this mission and so were the stakes for NASA, because a previous high profile mission (Mars Observer) had failed. But on September 11, 1997 MGS successfully arrived at Mars.

Artist Impression of Mars Global Surveyor

MGS was the first spacecraft to use a technique called 'aero breaking' to slow the craft down using the drag of the Martian atmosphere. This was done in April 1999 and MGS started its primary mapping phase of the Martian surface. Many thousands of images were beamed back in unsurpassed detail. At the same time, MGS was working as a relay station for missions on the ground, like the Mars Sojourner Rover and the currently still active Mars rovers Spirit and Opportunity. It also surveyed landing sites for future missions.

Originally MGS was scheduled to work for two years. But seen the recent failures of other Mars missions, NASA was nervous whether the craft would last that long. Needless to say, MGS outperformed NASA's wildest expectations lasting ten years instead of its designed two! It looks like MGS has finally reached the end of its rope. Since November 2nd nothing has been heard from the satellite and NASA has been unable to reesteblish contact. Even the newest mission, the Mars Reconnaissance Orbitor has tried to help, but was unable to locate MGS. NASA has not given up completely yet on locating and communicating with the MGS, but the outlook is grim.

A few of MGS' many important discoveries about Mars include:
(taken from NASA news release 2006-139)

• The spacecraft's camera found gullies cut into many slopes that have few, if any, impact craters. This indicates the gullies are geologically young. Scientists interpret this as evidence of action by liquid water, essentially in modern times.
  
  
• The mineral-mapping infrared spectrometer found concentrations of a mineral that often forms under wet conditions, fine-grained hematite. This discovery led to selection of a hematite-rich region as the landing site for NASA's Mars Exploration Rover Opportunity.
  
  
• Laser altimeter measurements have produced an unprecedented global topographic map of Mars. The instrument revealed a multitude of highly eroded or buried craters too subtle for previous observation, and mapped canyons within the polar ice caps.
  
  
• The magnetometer found localized remnant magnetic fields, indicating that Mars once had a global magnetic field like Earth's, shielding the surface from deadly cosmic rays.
  
  
• The camera found a fan-shaped area of interweaving, curved ridges interpreted as evidence of an ancient river delta resulting from persistent flow of water over an extended period in the planet's ancient past.
  
  
• A long life allowed Global Surveyor to track changes through repeated annual cycles. For three Martian summers in a row, deposits of carbon-dioxide ice near Mars' South Pole shrunk from the previous year's size, suggesting a climate change in progress.

Special Event

Tight grouping of Three Planets

On the morning of December 10th, the planets Mercury, Mars and Jupiter will be clustered together in a tight grouping. This will be the closest three planets will appear together for us in over 50 years.

Conjuntion of planets on the morning of Dec. 10

At the beginning of the month, Mercury is actually the highest of the three, rising less than an hour before the Sun. By the morning of the 10th, Jupiter and Mars have climbed closer to the fleet-footed wanderer. All three rise only one hour and fifteen minutes before the Sun on that morning. You will need a clear eastern horizon. This wonderful conjunction should be at its best around 40 minutes before sunrise. Viewing with a pair of binoculars will definitely enhance your experience.

If your sky is relatively dark, you might even be able to make out a double star just above and to the left of Mercury. This is Beta Scorpii, a twin-star system that represents the front part of the creature in the constellation Scorpius. By month's end, Mercury will have fallen from view while Mars and Jupiter climb higher each day.

Shuttle Discovery is a go for NightTime Launch

Space Shuttle Discovery is cleared for lift-off on the evening of December 7th (now delayed until Dec. 9th). This is the 20th mission to the International Space Station (ISS). The remaining missions to complete the ISS will be the most difficult and complicated for those crews.

Nighttime launch of Discovery October 11, 2000

The main task of this mission is to entirely rewire the electrical system for the ISS. The ISS has been running on a temporary electrical system since it went into orbit in 1998. So, finally after eight years, the ISS will get its permanent wiring done. This is no small task for the astronauts. They have two scheduled space walks as well as a multitude of tasks to perform from within the ISS. There are temporary solar panels that need to be folded up to make room for the permanent solar panels to rotate into their correct orientation.

The crew of this mission has been training for their tasks for the past six years. With the installation of two new electricity-generating solar array panels in September, all the pieces are now in place to switch to the permanent system. Lead Space Station Flight Director John Curry compared this to the way you might build a house on the ground - until your electricity is hooked up, you probably plug your saws into a generator. That's basically what the astronauts building and living on the station have been doing for the past eight years.

The launch window for Discovery extends until the 17th. NASA wants to have the shuttle and crew back down on Earth before New Years, because they are not certain the computer systems in the shuttle can handle the switchover from one year to the next. In all the years the shuttle has flown, there has never been a mission that has gone up one year and come down the next.

November 2006

Did you see the large fireball over Austin on October 22, around 10:20 pm? Or maybe you heard it: a loud rolling thunder sound? There have been many reports of exactly that! That Sunday evening, at 10:20 pm, just after the end of the concert of the Rolling Stones, a meteorite burned up over Austin and made its own spectacular fireworks. It traveled from East to West, and most sightings were in or around West Austin. The sound, which brought a lot of people outside, was described as thunder, and was loud enough to be heard inside. The thunderous noise was likely the sonic boom from the meteorite, because it travels much faster than the speed of sound. In addition to the sound, it left a trail in the sky, and apparently broke up in several segments; several people described seeing many trails. One person in Jonestown described seeing a large green ball. He was surprised this event was not widely covered in the media.

Events like this are relatively common, but definitely not a daily occurence. The Earth is bombarded by many thousands of meteorites each day. Most of them are the size of sand grains, or smaller, but sometimes they are substantially bigger. This meteorite was probably an inch or so when it entered the atmosphere. The larger the meteorite, the rarer they are. This is a good thing for us, of course, because if they get really large, they can reach the ground and potentially do a lot of damage. Meteor Crater in Arizona was formed by a meteorite of about 50 yards across. Impacts like that are, thankfully, exceedingly rare.

Victoria Crater on Mars.

Special Event

As you have read in the notes above about the planets, Jupiter, Mars, and Venus are all on the opposite side of the Sun. But, on November 8th, Mercury will be on the exact opposite side of the Sun from those planets, right between the Sun and the Earth. Mercury's orbit is relatively short compared to the Earth; a year on Mercury is just less than 89 days. So, Mercury passes between the Sun and Earth fairly frequently. This time however, Mercury will actually cross in front of the Sun, and we will be able to see a small black dot slowly transverse across the face of the Sun.

The reason that this does not happen every time, is that the orbit of all the planets are a little tilted. Some orbits more so than others, but just enough so that most of the time Mercury (or Venus) will cross just below or above the Sun - but not so this month. By the way, only three bodies exist that can pass in front of the Sun from our perspective: Mercury, Venus, and the Moon. The other planets are further away from the Sun than the Earth and cannot do the same 'trick'. Of course, if you happened to be on Mars, the Earth can cross in front of the Sun.

So what will be visible? Let's first start with a warning:

Never look directly into the Sun! NEVER, NEVER, EVER use a telescope or binoculars to look at the Sun. You will damage your eyes severely. Also, do not use a smoked piece of glass, or a CD to look at the Sun. It may feel like it is OK, but the Sun transmits other radiation (like UltraViolet rays) that will not be stopped, and will damage your eyes.

The only safe ways to observe the Sun is when it is projected, or to view it on TV.

Composite image 2003 Mercury transit

These days, transits like this one, are not terribly important. But in the seventeenth and eighteenth centuries, they were regarded as one of the most important scientific occurrences. You probably have heard about James Cook and his famous travels around the Earth. One of his main missions was observing a transit of Venus. The reason this was so important was because it presented a rare opportunity to measure the distance between the planets, and also measure the size of the Earth. Very precise measurements were needed, from different places on the Earth. So, they would observe the same transit from Europe, America, and Indonesia etc. Can you imagine traveling for six months or more, only to find the day of the transit it is cloudy? What a disappointment that would be.

October 2006

Pluto is not the first object in our Solar System to be down-graded from 'planet' status.

Last month, in this column, we talked a little about the recent reclassification of Pluto as a dwarf planet. In August, the International Astronomical Union (IAU) convened and decided on a new definition for a planet. One result of this change is that Pluto is no longer considered a major planet (please see last month's column for more details on Pluto and the new definition of a planet).

Johann Elert Bode (1747 - 1826)

Giuseppe Piazzi (1746 - 1826)

For the next few months, Ceres was heralded as the missing planet.

Then, in March 1802, another object was found. It was at about the same orbital distance from the Sun as Ceres. This came as a complete surprise to many people. They had just assumed that Ceres was the eighth planet - and that was that! However, they learned as we know, that that is not the case. For awhile, these objects were called small planets, but the number of the ones known grew large rapidly. In fact, at least one of these objects, now known as asteroids, has been discovered each year since 1801. As a result, Ceres was stripped of her 'planet' title within a few years of discovery. Even though Ceres is the largest asteroid, thousands of asteroids exist in the space between Mars and Jupiter - a region now termed the asteroid belt. Some of their orbits even go beyond Jupiter, almost to Saturn.

So, for over 200 years, we have known Ceres as an asteroid - until a few weeks ago. Two other objects were grouped with Pluto as dwarf planets with the recent redefinitions by the IAU. While Pluto's status was lessened, Ceres' was raised higher. No longer is Ceres just as asteroid. She is a mighty planet once again - albeit a dwarf planet.

In addition to the eight major planets, three dwarf planets are known in our Solar System at this point. Along with Ceres and Pluto, a third dwarf planet exists. This object was discovered in 2003 and initially named UB313, but also known popularly as Xena. This object has a new official name: Eris. Eris is slightly larger than Pluto and also has a moon, named Dysnomia. In Greek mythology, Dysnomia was the daughter of Eris, the goddess of discord.

Special Event

The Orionid meteor shower.

The Orionids should be at their best on the morning of the 20th, but will put on a good show through the 24th. You will need to stay up well past midnight of the 19th for good viewing. The Orionids seem to emanate from just north of the constellation of Orion.

An Orionid meteor

The Orionids, like their cousins the Eta Aquarids in May, come from a well-known source. Both of these meteor showers are a result of the Earth passing through the orbit of debris cast off long ago by Halley's Comet.

September 2006

Of course everyone has looked up to the stars in the night sky. Most of us can even name some constellations. But did you know you can also listen to the stars? That is the subject of this month's Did You Know.

Now, please do not run outside to see if you can hear a star making noise, because you will not hear anything. But stars are definitely noisy, and not just the stars. The whole sky is making a ruckus! If only you would have the right tool to change this noise into audible sound. The tool that we are talking about is a Radio Telescope.

The Compact Array, Australia Image © Friends of the Austin Planetarium

Next to light, the Universe is shining in all kinds of wavelengths, and one of those wavelengths is radio. So yes, if you can pick up this signal and plug it into an amplifier and loudspeaker, you can really hear noise. This will sound like static though, no pretty music or something. But sometimes, if you point the radio telescope right, you can truly hear some spectacular sounds. For example if you point it at a (Radio) Pulsar, you can clearly hear tick-tick-tick-tick.

But most of the time researchers are using radio telescopes to map an object to create pictures. There are some great benefits of a radio telescope over a normal telescope. The first one is that you do not have to wait until it is dark, because radio works during the day as well as during the night. Also, radio waves travel through interstellar clouds. For example, if you would like to 'see' what is behind the Orion Nebula, you can look through the nebula with Radio and see what is there.

As you can see from the picture above, radio telescopes are often working together. Because the wavelength of radio is so much longer then light, it is easier to combine signals from several radio telescopes making for all practical purpose a much larger telescope. Although radio astronomy does not produce beautiful pictures like the Hubble telescope does, it is an absolute essential cornerstone for astronomical research.

Special Event

As you have undoubtedly heard in the media, there have been made some changes to what is considered a planet, and Pluto is no longer considered a major planet, but a dwarf planet. But don't worry, Pluto is still there, and it is still a planet. FOTAP director Torvald Hessel was interviewed by News 8 Austin about this event. That video can be seen here.

So what happened? Why is Pluto no longer considered a planet? The thing is that for centuries we have struggled with the question, "what is a planet?". We have always known about the 5 naked eye planets (Mercury, Venus, Mars, Jupiter and Saturn), and for the longest time people just assumed that 5 was all there was.

Pluto & Charon Image courtesy of M. W. Buie (Lowell Observatory), D. J. Tholen (U. Hawaii), and K. Horne (St. Andrews)

Then in 1781 William Herschel discovered Uranus. At that time that meant a culture shock, because people were not even wondering if there were more planets, everyone knows there are only 5 right?

The result was of course that people started to study the Solar System in much more detail; if we missed one whole planet what else is out there? The result was the discovery of Neptune but also objects of the asteroid belt between Mars and Jupiter. First they were considered equal to the other planets, but when more and more objects were discovered, people started to call them 'Small Planets'. A book was published in 1898, and that has a list 434 'Small Planets'!

Soon after that, it was realized we cannot reasonably call them 'planets', and it was called the asteroid belt. So all was calm until 1930 when Pluto was discovered, and again the Solar System changed. Soon after the discovery we found that although Pluto was larger than anything in the asteroid belt, it was different than the other planets. But what to call it other than a planet, especially when in 1978 Pluto was discovered to have a moon (Charon)? We all thought the discussion was over; Pluto was a planet.

But the discussion started anew when new objects were found even further away than Pluto. And what's more, these objects shared characteristics with Pluto much more then with the other planets. This discussion finally culminated in the decision taken last month by the International Astronomical Union that defines a planet as follows:

• It must be in orbit around the Sun
• It must be heavy and large enough, so the shape is spherical
• It must have cleared it's orbit from other objects

The last statement disqualifies Pluto as a (major) planet, because it crosses Neptune's orbit. So, now we have 8 Major Planets, and three Dwarf Planets. Can you name them already? They are Ceres, Pluto and UB313 (or unofficially Xena).

August 2006

Astronomers of all kinds like to throw a party. This party doesn't involve bright lights or a bunch of noise. This party requires some telescopes (the more, the merrier), a group of people who appreciate the stars and planets and a nice, quiet dark sky (the darker, the better).

This kind of party is called a Star Party. People from all walks of life and all ages are welcome at this party. People who know just a little or nothing about astronomy are very welcome here. People who know a lot about astronomy are at the Star Party and are very willing to share the eyepiece of their telescopes and teach others about the fun and science of astronomy.

The Austin Astronomical Society and St. Stephen’s Episcopal School is throwing just such a party during the month of August. Please mark your calendar for August 12, a Saturday, for "Austin Under the Stars" at St. Stephen's School.

The Friends of the Austin Planetarium will be there with our StarBubble. The StarBubble is a portable planetarium that can hold 20-25 people. It will be set up inside a comfortable, air-conditioned room and even has its own air-conditioner attached directly to it. Every 20 to 30 minutes you can catch a free presentation. This will give you an idea of how wonderful it is to experience a planetarium. We will also have koozies and mugs available. Come by and find out how you can get one! We'll be glad to talk to you about what you can do to help bring a planetarium to Austin.

The event runs from 6:00 p.m. until midnight. Solar viewing and planetarium shows begin at 6:00 p.m. with the star party kicking into gear at about 8:00 p.m.

See ya there!

Special Event

There are three special events this month - two occurring on the same night!

The conjunction of planets in August, though low in the sky, should be quite spectacular.

On August 10th and 11th, looking east-northeast about an hour before sunrise, you should see Venus right above Mercury (see Mercury and Venus in the Planets section above).

The conjunction of Mercury, Venus, Saturn and the crescent Moon on the mornings of the 21st and 22nd should be a memorable sight (see image below). Also, Venus and Saturn are at conjunction on the mornings of the 26th and 27th. See Saturn in the Planets section above for more details on these events.

Conjunction of planets and moon on August 22nd

The other two events are the Austin Under the Stars (AUTS) star party (details in the Did You Know section below) and the Perseid Meteor Shower.

The peak of the Perseids occurs on the night of the 12th. The good news is that that date is also the date of the star party, so come out to AUTS and you might see a shooting star as you walk from one telescope to the next. The bad news is that the Moon is just three days past full on the 12th. That means he is still more than 90% full. The Moon will rise at 10:33 p.m. and not set until the following morning. The best times for viewing the Perseids is well after midnight, but you could see some before moonrise.

July 2006

In astronomy, and hence in this AstroNews column, we often talk about how bright something is. Venus is brighter than Mercury, and an Iridium flash can be many times brighter than Venus. To truly indicate how bright something is you need a term to describe this. In astronomy we use magnitude.

Hipparcos, CA 190 BC - 120 BC

The first person that we know of that made a list of stars and how bright they appeared was Hipparcos. Hipparcos lived from about 190 BC to 120 BC, and his list consisted out of 1080 stars. Taken the fact that the telescope had not been invented, these were all stars visible with the naked eye. Hipparcos separated the stars into 6 groups of different magnitude, where group number 1 contained the brightest stars and 6 the dimmest. So, the larger the number, the dimmer the star!

The basic idea of this scale we still use today. About a century ago, scientists discovered that these 6 groups followed a mathematical law. Without going into specifics here, it became possible to truly calculate magnitudes and to measure them electronically. Because Hipparcos did everything with the naked eye, when calculated some of the stars actually became magnitude zero, or even negative! For example, Sirius, the brightest star in the sky, shines at magnitude -1.6. We can also calculate that the Sun shines at magnitude -26.7. Do not make the mistake though, to think that the sun is -26.6 / -1.6 = 16.7 times as bright as Sirius. This scale is a logarithmic scale, the difference between magnitude -1.6 and -26.7 is more than 10 billion!

Another example is the Iridium flash from June; this flash had a magnitude of -7.4. The planet that can be the brightest is Venus. The maximum magnitude of Venus is about
-4. That means thatthe flash was about 40 times as bright as Venus ever can be. Quite a flash indeed!

Special Event

Iridium
Another interesting thing to look for are Iridium satellites. These satellites have very large solar panels, and if you are at the right spot at the right time, you can experience an Iridium 'flash'. The satellite will reflect the sunlight for a short time, so it's like a star that pop's up from nowhere, then becomes very bright, and then it disappears again, all in the matter of seconds.

Because the Iridium satellites are in regular orbits, you can also plan for an Iridium event. Check out this page to see if any will be visible. There was one on June 28 that was many times brighter then for example Venus ever can be. Drop us a line if you are flashed by Iridium!

June 2006

Did you know you can see moon craters, double stars, and planet disks with just a pair of binoculars? That's right! Those are just a few of the myriad of different things you can see up in the night sky without a telescope. You should have little trouble spotting Jupiter's four Galilean moons; a number of globular clusters will open their doors to you when you put your eyes behind a set of binoculars and point them skyward.

A good set of binoculars is fairly easy to come by and is typically a lot less expensive than a reasonably good telescope. You (or someone you know) might already have a pair stashed away in a drawer or the back corner of a closet. If that's the case, then you won't have to spend an extra penny to get started with looking more closely at the night sky. Just be sure to ask permission to use them if they are not yours.

Binoculars are usually described by two numbers, such as 8x35 or 10x50. The first number is the power of magnification, while the second number is the diameter of the front lens in millimeters (mm). The second number is important for us, because it represents the light-gathering capacity of your binoculars. This translates into how bright objects will appear in your binoculars. For example, a 10x50 pair of binoculars would make things seem 10 times closer. With a little math, we can calculate that our 50 mm front lens has 1963.5 square mm of light-gathering power. How does this compare to your eye? We know that the average diameter of the human pupil in dark conditions is 7 mm, so the light-gathering area for one eye is about 38.5 square mm. That means viewing with binoculars gives your eyes about 50 times more light.

For astro-gazing, you will want to stabilize your binoculars as much as possible, especially for any power above seven. Ones that attach to a tripod work the best, but you can easily brace the binoculars to something stable like a building, car, or a big rock. Go to the darkest patch of sky you can get to on a clear night when the humidity is low and you will be in for a real treat.

Clearly (pun intended), getting started with a pair of binoculars can be fairly inexpensive. The results are instantly rewarding when you take them out on a clear, dark night. Also, this allows you can save your money longer to eventually buy a telescope. The longer you save, the bigger and better the telescope you can afford. In the short-run, you have a set of optics that will get you out at night on a regular basis.

Special Event

If you look to the West at sunset over the first two weeks of June, you will see Saturn and Mars getting closer together each evening. By the evening of the 15th they are quite close indeed, but there is an additional treat in store. With the aide of a pair of binoculars or a small telescope you will see Mars appear to be exploding from the globular cluster known as Praesepe or the Beehive Cluster. This group of stars is about 600 light years from Earth and is about twice as old as our solar system. The striking orange of Mars should provide an interesting contrast to the soft, silvery points of the Beehive, like a lone red wasp in an otherwise quietly humming hive.

On the evening of the 17th, we are in for an even sweeter treat. Look low in the West, again at sunset, and you will see Saturn and Mars seemingly next to each other,

Conjunction of planets on June 17th

almost one atop the other. If you hold your arm out straight and cover Saturn with your little finger, you will easily cover Mars as well. The Beehive Cluster is still very close, just a tad to the right of the planetary pair. While Saturn and Mars have gotten closer to each other, Mercury has climbed out of the sunset glow to make one of his best appearances of the year. He can be found lower and to the left of the bright twins, Castor and Pollux in the constellation Gemini. By the 20th, Mercury climbs even higher reaching greatest elongation from the Sun. What a truly spectacular event: three planets and one globular cluster! Take your binoculars or telescope out to the darkest location you can get to with a good western horizon. The weather should cooperate by mid-June, so be ready to enjoy the view and be truly impressed by the vastness that surrounds us.

May 2006

An opposition is always the best time to observe a planet, because during opposition the planet is at its closest approach. For example, Jupiter will "only" be about 365 million miles from the earth. Of course this is still a lot, but compared with a distance of almost 800 million miles at its furthest from Earth, 365 doesn't sound that bad.

This image of Jupiter was taken by the Cassini Spacecraft when it flew by Jupiter. Image courtesy NASA

April 2006

As you might have noticed, there is a lot going on, on Mars. Did you know there are currently five active missions on and around the Red Planet? Since the arrival of the Mars Global Surveyor, the number has been steadily increasing. Currently we have:

1. Mars Global Surveyor
2. Mars Express
3. Mars Exploration Rovers
4. Mars Odyssey
5. Mars Reconnaissance Orbiter

Actually we can say there are six missions, but the two rovers, Spirit & Opportunity, we count as one. To the right you can see a slide-show of the five missions. All images are taken from the various Mars mission pages and are courtesy NASA/JPL.

Below you can read about the five spacecrafts that are currently active in, on or around Mars. Of course, each mission has its own NASA website with a wealth of information, so we will include a link to the appropriate sites. The list is in chronological order.

• Mars Global Surveyor
  The Mars Global Surveyor (MGS) has been in orbit for more then 3000 days now, and is still going strong. MGS arrived at Mars in 1997 after a 20 year hiatus of having a spacecraft at the Red Planet. For almost a decade MGS has been orbiting the planet and taking amazing images. Actually, MGS will fill a crucial role in the newest mission the Mars Reconnaissance Orbiter. It will monitor the weather, which is very important for the successful earobreaking. It will also assist in finding landing sites for future missions, and of course MGS will continue to map the surface of Mars. The NASA site for the MGS mission you can find here.
  
  
• Mars Odyssey
  Last November it was two years since the Odyssey mission arrived at Mars. The Odyssey mission is also an orbiter but with a totally different function then the MGS mission. Odyssey is able to measure many elements on the surface and in the atmosphere of Mars. Odyssey discovered vast amounts of water ice in the polar regions. It also records radiation levels which is very important to know if we ever will undertake a manned mission to Mars. In addition to this, the Odyssey is also working as a relay station for data from the two rovers on Mars (see below). The NASA site for the Odyssey mission you can find here.
  
  
• Mars Express
  This mission is a joined NASA/ESA mission and was originally consisting out of two parts. It contained a lander (the 'Beagle 2') and an orbiter. The lander was designed to do very detailed rock and soil analyses and many hoped it would be able to settle the question whether life exists on Mars. Unfortunately, the lander was never heard from again, and probably crashed on the surface of Mars when it attempted to land.
  However the orbiter has been a great success and is still active. One of its latest discoveries is direct prove for underground (water) ice. The NASA site for the Odyssey mission you can find here.
  
  
• Mars Exploration Rovers
  We are sure you have heard about the two little Mars rovers that are riding around on the surface of Mars: Spirit and Opportunity. Because it is so difficult to reach and land on Mars, NASA decided to send two missions to raise the stakes that at least one is successful. This time we got very lucky, because both rovers arrived successfully. (The rovers arrived in the same year as the Mars Express which was not so lucky on the landing) Spirit and Opportunity have gathered an enormous amount of geological data, and are still going strong. We're sure that these two rovers will make more amazing discoveries and beautiful pictures of an alien landscape. The NASA website of the two rovers you can find here.
  
  
• Mars Reconnaissance Orbiter
  The Mars Reconnaissance Orbiter (MRO) arrived last month at Mars, and the trickiest part, the orbital insertion, was successful. When a spaceship arrives at Mars, its speed is much too fast to go into orbit. So, at the correct time the ship will have to start firing a rocket to slow itself down. This is always a tricky phase of the mission, because part of it will take place behind Mars and we loose contact with the ship. So, all these steps have to be automated. But again, everything worked as it was designed, and the MRO is in orbit around Mars. But we're not done yet! Currently the orbit of the MRO is a large ellipse, and it needs to become a circle. What NASA is going to do, is to use the Martian atmosphere to slow the craft down. This was done successfully with the Global Surveyor. This process will take about 6 months, and the MRO will have to fly through the atmosphere about 500 times to slow it down just enough. But if it dips too deep in the atmosphere it will burn up. So there are still some tricky maneuvers left.
  
  But when all is set and done, we will have an amazing spacecraft in Martian orbit that will undoubtedly change our view of Mars entirely. If everything on the MRO works as designed, MRO will return more data back to earth then all previous missions combined. The NASA website of the MRO you can find here.
  
  

Special Event

This is not a joke! On the first of April, the Moon will occult the Pleiades. So what exactly does this mean? You might know, or even know how to find the Pleiades. The Pleiades are a small grouping of stars that is rather striking. With the naked eye about 6 or 7 stars are visible, but with a telescope many more are visible. The Pleiades are what Astronomers call an open star cluster. The stars from the Pleiades are all formed around the same time, and from the same cloud of gas many millions of years ago. But they are indeed like family members all at approximately the same distance.

Of course the Moon is much closer to the earth, and sometimes blocks the light from another star. The most spectacular example of this is of course a Solar Eclipse, where our Moon occults the closest star: our own Sun. But on April first, the Moon will slide in front of the Pleiades, occulting the stars one by one. A little later of course, they will re- appear on the other side.

Also, as is clear from the calendar above, the Moon is not even half lit yet. About a quarter of the moon will be visible. The dark sight will cover the stars first, and they will re-appear from the light sight. Also, for this event you do not need a telescope, although binoculars will help, because you will be able to see more stars from the Pleiades.

To find the Pleiades on the first of April is of course very easy: all you have to do is to find the Moon. The bowl of the Moon will point right at the Pleiades. The first stars will start to disappear around 6 pm. So the start of this event will not be too ideal for us in the Austin region, because it will be still rather light. But as the evening progresses, we can still have a nice show.

March 2006

The Earth is actually closer to the Sun during our Winter? Strange, but true! Let's look at why.

An elliptical orbit. The small dot in the sun is the actual center of the ellipse.

The Earth's orbit around the Sun is not circular - it is slightly elliptical (somewhat egg-shaped). The Sun is a little bit off of center of this ellipse (it actually lies at one of the two focal points). During January the Earth and the Sun are at their closest to each other. The Sun is actually brighter in the sky during January. This increased brightness goes unnoticed though. Since the Sun is lower in the winter sky, its rays pass through a greater thickness of atmosphere, easily canceling any brightening we might experience.

The earth's axis of rotation is tilted 23.5 degrees from the plane in which it revolves around the sun (see diagram below). Back in December, on the winter solstice, the North Pole reached its greatest tilt away from the Sun. Likewise, on the summer solstice in June, when the Earth is at the opposite side of her orbit, the North Pole will be leaning most directly toward the Sun. Correspondingly, the South Pole is tilted its greatest toward the Sun in December and has its maximum tilt away in June.

So, you might think that the southern hemisphere would endure hotter summers and colder, harsher winters compared with their northern counterparts. The combination of these two effects, being closer to the Sun and being tilted more directly at the Sun, should make for warmer summers and more frigid winters. In fact, the combined effect is not too noticeable. This is due to the large stretches of ocean that cover the southern hemisphere.

A representation of the tilt of the earth's axis in relation to the sun.

However, the current situation has not always been the way of things. These two factors may have combined to produce ice ages in the past. The ellipse that is Earth's orbit gradually rotates around the sun. Like a rubber band being twiddled between two fingers, it completes one total revolution in approximately 23,000 years. This means that over time, the North Pole will eventually be leaning away from the Sun at point in the Earth's orbit when it is furthest away. This could lead to increased glacial activity as in previous ice ages.

For right now, we are at a pretty even balance, so don't go buy a snow blower just yet.

Special Event

On March 10th, the Mars Reconnaissance Orbiter (MRO) arrives! This spacecraft from NASA, launched in August of last year, will spend the next several years studying the history of water on Mars. It's many science instruments and powerful cameras will allow MRO to get an extreme close-up look of many regions on Mars. Click here to visit the MRO home page.

The Full Moon will rise on March 14th, already being eclipsed by the penumbral shadow of the Earth. This should give the Moon an eerie darkening or shading, but you will still be able to see it. This is one of only five times all century that the Moon will lie completely in the penumbral shadow of the Earth. NASA has a wonderful web page with details on all solar and lunar eclipses during 2006.

The Vernal Equinox marks the beginning of Spring in Central Texas, and the rest of the Northern Hemisphere. We all pray that this will mark an end to the severe draught we have been suffering through as well. While the draught has given star gazers many wonderfully clear nights with low humidity, enough is enough! Our trees and vegetation desperately need a deep soaking.

For a more detailed explanation of the equinox, please visit the March 2005 edition of the AstroNews.

February 2006

Last month we wrote about how old you would be on another planet, and we found that each planet rotates at a different rate than Earth. But, because each planet differs in size you will also weigh a different amount. You might have seen pictures from the moon missions where the astronauts can make spectacular jumps even wearing their heavy and bulky suits. The reason is that the gravity, the force that pulls you down to the floor, is different on each planet. A lighter planet will have much less gravity then a heavier one. Taken the fact that the moon is much smaller than the Earth you will weigh much less as well.

If you are curious what you will weigh on another planet, we have built a small 'calculator' below. Just type in your weight in the first box, then select a planet and the calculator will tell you what you would weigh. In addition to all the planets, we also put in the Sun and some moons as well. Have fun exploring!

Special Event

This month there are no great astronomy events visible to the naked eye. But of course there is always plenty to see! Of course you can see many stars, but did you know you can spot satellites? There are hundreds of satellites currently circling our planet and under a moderate dark sky you can see one every couple of minutes. A satellite will look just like a star, but it will move quite rapidly among the stars on a straight line. There should be no green or red flashing visible because then you are seeing a plane. However, certain satellites rotate and then the solar panels or any other reflective surface will show intermittently. Then you see a blinking star, like a traveling blinker through the sky.

Early next month though, the Friends of the Austin Planetarium will be present at the Zilker Park Kite festival. This year the festival will be held on the 5th of March. We will have a cosmic wheel of fortune and will give away prizes. If Lady Luck is with you, you might have a chance to win the Grand Prize: a beautiful telescope! Come check us out on March fifth!

January 2006

Each planet in our solar system goes around the Sun in a different amount of time than the Earth. Of course a year is the time it takes for a planet to go all the way around the Sun once. So, each planet's year is shorter or longer than that of the Earth. The Earth takes about 365.25 days to go around the Sun once. (Note: we will just talk about Earth days. Each planet also has its own length of day, so things could get a bit confusing if we try to take on too much at once.) The planets closer to the Sun have a shorter year than the Earth, while the ones further from the Sun have a longer year.

Here is a chart showing (in Earth years) how long it takes each planet to go all the way around the Sun once:

Consider this: you would be a different age on the other planets. I have a friend who is turning 41 in January. That's 41 in Earth years. She would already be over 66 in years on Venus, but still be less than 22 years old on Mars - and less than 4 years old on Jupiter. So, take your pick: retired, in college, or still a pre-schooler with these extra-terrestrial ages. Using the chart above and the following formula, you can easily calculate your own age in each planet's years:

X = Your current age
Y = Any number from the chart above

X / Y = Your age in another planet's years

Are you an old wo/man on Mercury? Still an infant on Saturn?

Speaking of Martian years, the two Rovers, Spirit and Opportunity, recently celebrated their first Martian year, November and December respectively. Spirit will mark two full Earth years on Mars on January 3rd. Not too bad considering their original mission goals was 90 Earth days each. They have now been on Mars around 700 Earth days each.

Here is a link to the Rovers' home page to see what they are currently doing.

Special Event

Earth is at perihelion on January 4th. This is the closet that the Earth gets to the Sun each year. As you may know, the Earth goes around the Sun in an elliptical orbit and not a perfect circle. So, six months from now we will be at our furthest from the Sun. On the 4th, the Earth will be 147,103,622 kilometers from the Sun.

You may wonder how can we be closest to the Sun during Winter and furthest from the Sun in Summer. We will talk about that for our Did You Know section in March. But remember, it is Summer for our friends who live in the Southern Hemisphere right now.

Happy New Year to all and let's hope that 2006 sees some major developments toward a planetarium in Austin becoming real!!!

December 2005

An early philosopher created a ranking of the sciences, and in his opinion the most worthless science was Astronomy. He said that because he believed that it would be forever impossible to find out what a star was made of because we would never be able to reach one.

Although, he might be right on the fact that indeed we are unable to travel to another star, he was not right in thinking that we never would be able to discover what stars are made of. We know in great detail what stars are made of and how they are able to produce so much energy for such a long time. The secret to this knowledge is spectroscopy. It would be quite beyond the scope of the AstroNews page to explain in great detail what spectroscopy is, but one very simple concept we can use even with the naked eye.

When something gets hot, it will start to glow. For example a piece of metal will start to glow red when you hold it long enough in a flame. Hence the term 'red hot'. But when we make it even hotter, it will start to shine more towards orange and then yellow. It will also look brighter because our eyes are more sensitive to yellow then to red. So we can say that 'yellow hot' is hotter then 'red hot'. Of course, when we keep heating the piece of metal it will melt. The point we would like to make is that the color is a direct indication of temperature. We can use this to classify stars.

When you look at stars you will notice that they do not all have the same color. Some are obviously reddish and others more blue colored. A good collection of stars is the constellation of Orion. Betelgeuse, in the top left corner of the constellation, is a red-colored star. It shines at a temprature of about 6000 degrees Fahrenheit (3600 Kelvin). However, the stars in the belt of Orion are whitish blue, and therefore much hotter. They shine at a dazzling 90,000 Fahrenheit (50,000 Kelvin). Another good example is our sun, neither red nor blue but a nice yellow. The temprature is indeed in between as well: about 11,000 Fahrenheit (6273 Kelvin).

So, although we are not able to travel to the stars, we are able to tell very simply the tempreatures of the stars. The temperature in turn tells again something about the size and weight of a star, and even its age. Pretty amazing indeed, that without traveling or touching we are able to tell so much of objects that are lightyears away!

Special Event

The winter still has to begin in Central Texas, but after December 21 the days will become longer again, and we are "gearing up" towards spring. Of course the coldest months, January and February, are yet to come but it will be pleasant to have more daylight.

A longer night though, does give us some benefits; we do not have to get up terribly early to see something while it is still dark. For example, to see Mercury this month we only have to get up around 6-6:30. If this would have been in the summer, we would have to get up several hours earlier.

Other than Mercury, there is not that much going on in the sky this month. There is a meteor shower on the 13th, the annual Geminid meteor shower, but the Moon will be a spoiler. Because of the light from the Moon will make most shooting stars invisible.

November 2005

The Leonid meteor shower reaches its peak on the morning of the 17th. They seem to originate from the constellation Leo, hence their name. Their true source is the comet Temple-Tuttle, which orbits the Sun about every 33 years.

When a comet gets close to the sun, millions of tiny particles are thrown from the comet, thus creating a big path of these particles. The Earth's orbit happens to pass through a small part of this path. When one of these particles (usually no bigger than a small grain of sand) enters the Earth's atmosphere, it burns up. Because the Leonids are moving at such a high speed in relation to Earth, a number of these meteors leave a long vapor trail.

Comet Temple-Tuttle was nearest the Sun in 1998. The following four years were quite spectacular for viewing the Leonids. People were seeing thousands of meteors within an hour's time. This year we should expect anywhere from 15 to 100 meteors per hour, which is still quite impressive. However, the Full Moon just two days earlier will be a bit of a hindrance.

You might remember that this comet was in the news earlier this year when NASA slammed a large metal "bullet" into its surface on July 4th. The mission was called Deep Impact and was a huge success. NASA has learned a great deal about comets from the mission. You can learn more about Deep Impact by visiting the official Deep Impact website.

Special Event

For some reason everything to do with Mars is always hyped. Probably this is because Mars shines so obviously red in the sky. Mars was known as the God of war, undoubtedly for its 'blood' color. Well, Mars is red and this is indeed clearly visible to the naked eye this month, but it certainly is not as red as blood!

Unfortunately, because of all this hype observing Mars for the first time is often a big disappointment. These days we are dazzled by amazing Hubble pictures and also close up images of Mars from all the orbiters around this planet. By seeing these images, people assume that when they look through a telescope, they will see something similarly spectacular. Then, when they see a brownish-reddish blurry picture with some white spots and some lighter and darker areas, people are disappointed.

Mars as seen through a telescope. Image taken from Astronomy Picture of the day 26 August 2003.

The trick is to know what to expect when you look through a telescope. Just the very fact you can see some surface features at all with even a very small telescope, is quite spectacular. The image to the left gives you a very good idea how Mars would look like through a telescope.

As you can see the image is wobbling and quite blurry. This is because of the movement of air in the atmosphere. The worse this is, the worse the seeing is in a telescope. You can see several features of Mars. You can see the south polar cap and darker and lighter areas. With a good map of Mars you will be able even to name some of the features visible!

The trick is to have patience when observing. There are times when all of the sudden the seeing is perfect, and for that short time you are able to see much more detail. It also takes (a lot of) practice. Good luck observing Mars this month, and if you have something to share about your experience, please let us know and we may publish it on next month's Astro News.

October 2005

As you know, the Earth rotates around the Sun just like all the other planets of our Solar System. But the further a planet is away from the sun, the lower it's velocity. Also, if a planet is further away from the Sun, the circle it describes is larger. Therefore the further a planet is from the Sun, the longer it takes to complete one circle around the Sun. Taken the fact that the Earth is closer to the Sun then Mars, we are rotating faster and every two years we pass Mars. This point of closest approach is called 'opposition'. For the Earth and Mars this happens approximately once every two years.

But the story does not end there. Both the orbit of the Earth and Mars are not perfect circles: they are ellipses (elongated circles). Mars has an orbit much more elongated than the Earth, and in comparison we can say that the orbit of the Earth is circular. Due to the eliptical nature of especially Mars' orbit, the point of closest approach is not necessarily at the same day as the opposition. This year, the closest approach is on October 29, the real opposition is not until 8 days later: November 7.

Another effect of the elongated Mars orbit is that not every opposition is as close as the other. Below we have drawn two extremes, one as close as possible and one as far as possible:

Schematic representation of the orbit of the Earth (blue) and Mars (red) around the sun (yellow).

As you can see there can be quite a difference in Mars/Earth oppositions! This year we have a better then average opposition. The coming 6 oppositions will be less then the one from this year; so we have to wait about 13 years for another opposition as good as this one. However, the opposition from 2003 was almost perfect. We would have to wait something like 60,000 years before we will see another approach of Mars that is that close. So, although this years approach is less than the one of 2003, Mars will still be spectacular to observe.


The following is a repeat from last month's Astro News

We have received many questions about the Mars oppositions in October. These questions mostly relate to an email that has been going around making some eyebrow raising statements. Interestingly enough the email is a mix of almost correct statements and one very unfortunate typo. First of all the letter states that Mars will be at its closest at August 27, and this is the closest that Mars will be in something like 60,000 years. What is being referred to is the Mars opposition from 2003, not 2005. Indeed in 2003 we had a very close opposition for Earth and Mars. This year it still will be above average, but not as good as in 2003. So that is the first mistake.

The second mistake in the letter is due to a very unfortunate typo... These two sentences appear in the letter:

• At 52x magnification.
• Mars will be as big as the Moon!

The unfortunate thing is that these two sentences were originally ONE sentence. Indeed at the proper magnification Mars will be as big as the Moon. Needless to say, Mars will *not* be as big as the Moon in our sky. So if you receive this email from family or friends you now know what to tell them!

September 2005

Of course you know that the sun rises in the East and sets in the West, but not only sun does that also the moon rises in the East and sets in the west. In addition the planets do exactly the same! Almost all the objects from our solar system make the same apparent path through the sky: from East to West. The reason for this is that our solar system is flat, all the planets rotate in a disk (or a plane) around the sun and all the planets rotate in the same direction.

A representation of the ecliptic and the apparent path of the sun

The path that the planets and the moon follow is called the ecliptic. The moon nearly follows this path as well, but strays above and below it in the time (almost a month) it takes to go around the earth once. During this time, the moon crosses the ecliptic twice. From the Greek word for ‘failure to show up’ an eclipse happens when the sun, moon and earth form a straight line as the moon crosses the ecliptic. If the order of the line is sun-moon-earth, we have an eclipse of the sun – or solar eclipse. This is when the moon’s shadow is on the earth. If the sun-earth-moon line up, we have a lunar eclipse – the earth’s shadow is cast onto the moon. With either of these situations, a full or partial shadow is present. If the alignment is exact, then we have a total eclipse.

As you may know, the earth is tilted on its axis (about 23.5°) in relation to its path around the sun. The angle of tilt can be seen on most globe atlases of earth. This tilt defines how big the Arctic and Antarctic Circle is at each end of our planet. Each region is tilted away from the sun for six months and tilted toward it the following six months. This, of course, is the reason each polar region has half year of light (i.e. the ‘Land of the Midnight Sun’) and a half year of darkness. The autumnal equinox marks the first day the sun shines at the South Pole, and the beginning of six months of darkness at the North Pole.


We have received many questions about the Mars opposition in October. These questions mostly relate to an email that has been going around making some eyebrow raising statements. Interestingly enough the email is a mix of almost correct statements and one very unfortunate typo. First of all the letter states that Mars will be at its closest at August 27, and this is the closest that Mars will be in something like 60,000 years. What is being referred to is the Mars opposition from 2003, not 2005. Indeed in 2003 we had a very close opposition for Earth and Mars. This year it still will be above average, but not as good as in 2003. So that is the first mistake.

The second mistake in the letter is due to a very unfortunate typo... These two sentences appear in the letter:

• At 52x magnification.
• Mars will be as big as the Moon!

The unfortunate thing is that these two sentences were originally ONE sentence. Indeed at the proper magnification Mars will be as big as the Moon. Needless to say, Mars will *not* be as big as the Moon in our sky. So if you receive this email from family or friends you now know what to tell them!

Special Event

This month's special events are related: the Autumnal Equinox and the Harvest Moon.

The Autumnal equinox marks the beginning of fall in central Texas and the rest of the northern hemisphere. At this point we can officially begin anticipating cooler weather :-). On both equinoxes (there is one for spring as well) night and day are equal. In fact, the word equinox comes from Latin, meaning ‘equal night.’ After the autumnal equinox, nights become longer and days become shorter all the way until the winter solstice in December. Equivalently, days become longer with the advent of the Vernal (spring) equinox. These events are opposite for the southern hemisphere.

The Harvest Moon is just the name we give to the full moon closest to the autumnal equinox. As with every full moon, the harvest moon rises right at sunset. During the year – on average – the moon rises 50 minutes later each evening. The harvest moon rises only about 25 minutes earlier each night for several nights, thus keeping after twilight darkness at bay for at least an extra week while the moon is fat. This was important to farmers gathering crops in the many centuries before electricity. These days it helps us forget – for a little while – that the days are truly getting shorter. The reason the Harvest Moon rises just 25 minutes later each night is because the moon’s path is closest to the ecliptic (see the Did You Know section below) at this time of year.

August 2005

The first true visionary of space travel was undoubtedly Jules Verne (1828-1905), but the first person to actually tackle the science of this subject was Konstatin Tsiolkovsky. He was born in Russia in 1857 and was home schooled until age 16. He was not accepted at the local grade school, because he was deaf. Despite this, he became intrigued in rocketry at a very young age.

Playing with a balloon when he was about 12 years old, he understood why a balloon flies away when released. When a balloon is at rest, the air inside will press equally to all sides and the balloon will not move. But when there is an opening the air on the opposite side has no opposite counterpart anymore and will propel the balloon forward. He also realized that this would work in a vacuum. Actually, it would work better in vacuum because there is no air resistance to hold back the balloon! So, unlike most people think, the balloon does not propel itself because of the air that rushes out of the balloon.

He further theorized, that if you would be able to keep the air somehow in the balloon under high pressure, the balloon would keep flying. This was how he came upon the idea of a rocket engine powered by liquid fuel.

At age 16, his dad sent him to High School and University. Tsiolkovsky, eventually became a math teacher, but in his spare time he spent most of his time thinking and writing about rocketry. This was of course not understood by his surrounding and he was often mocked because of his “crazy” ideas.

Being a math teacher, he also developed formulas that describe rockets and rocket engines. He even figured out that you would need a multi stage rocket to reach the moon. The basic equation for rocket propulsion, the Tsiolkovsky rocket equation, is named after him.

When he was 60 years old, the Bolshevik Revolution took place. Unlike the Tsar, the Soviets did realize his brilliance and he became a member of the Academy of Science. Between 1925 and 1932, 60 of his papers were published.

Tsiolkovsky envisioned it all: satellites, people in space, manned space stations, manned missions to the Moon and Mars and populated space colonies in high Earth orbits. On his grave stone are his most famous words: “The Earth is the cradle of humanity, but men cannot stay in their cradle forever”. Tsiolkovsky died in 1935.

Special Event

Happy Birthday Astro News!
This month's issue is exactly one year after we started with writing the Astro news page. We have received many positive reactions, and we sure have a lot of fun writing these pages. We sincerely hope that there will be many more Astro News pages to come!

Every two years when Mars and Earth are at their closest point, the time is ideal to launch a spacecraft to Mars. During that time it takes the least amount of energy to travel to Mars, and for the past years NASA has used this opportunity every time. This time MRO will be launched. MRO stands for Mars Reconnaissance Orbiter, by far the largest spacecraft ever sent to the red planet. This satellite will not land on the surface of Mars, but it will do its research from above the Martian atmosphere. It will search for water, and will be able to take high resolution images. If all goes well, we will sure learn a lot more about the red planet. The official MRO website you can find here.

On August 12 we experience our annual Perseid Meteor shower. Although the moon is about half, it will set before most of the activity will take place leaving us with a perfect dark sky. There are also some predictions that this year we might see some extra activity lasting a couple of hours. These predictions are getting better each year so that is something to look out for. This peak is expected around 4 a.m. on the morning of August 12th.

In last year's astro news we detailed exactly how to observe this meteor shower, so instead of repeating ourselves, you can look it up using the pulldown above the calendar to go back to last year's news.

July 2005

Astronomers of all kinds like to throw a party. This party doesn’t involve bright lights or a bunch of noise. This party requires some telescopes (the more, the merrier), a group of people who appreciate the stars and planets and a nice, quiet dark sky (the darker, the better).

This kind of party is called a Star Party. People from all walks of life and all ages are welcome at this party. People who know just a little or nothing about astronomy are very welcome here. People who know a lot about astronomy are at the Star Party and are very willing to teach others about the fun and science of astronomy.

The Austin Astronomical Society and St. Stephen’s Episcopal School is throwing just such a party during the month of July. Please mark your calendar for July 16, a Saturday, for "Austin Under the Stars" at St. Stephen’s School.

The Friends of the Austin Planetarium will be there with our new StarBubble. The StarBubble is a portable planetarium that can hold about 20 people. It will be set up inside a comfortable, air-conditioned room. Every half hour you can catch a free presentation. This will give you an idea of how wonderful it is to experience a planetarium. We will have koozies and mugs available. Come by and find out how you can get one! We’ll be glad to talk to you about what you can do to help bring a planetarium to Austin.

Please note that due to inclement weather this event has been rescheduled till August 13! Maybe Mother Nature will be kinder next month – please join us at St. Stephen’s on August 13, 2005!

Special Event

Two very important items of special interest occur this month. They both reflect the human pursuit of science and our presence in space.

On the evening of July 3rd (actually the morning of July 4th), Project Deep Impact will reach its destination with a visual display worthy of a Fourth of July fireworks celebration. At about 12:52 a.m. Austin time (so that’s a little after midnight) a projectile will impact on the surface of a comet. You might even be able to see the flash at impact using your own telescope. Comet 9P/Temple 1 will become the focus of new discoveries as we look at the effects of smashing an 820 pound bullet into a large, dirty snowball at a speed of 23,000 miles per hour! This will not destroy the comet at all, but by observing the comet before and after the impact we will learn a tremendous amount about what a comet is made of. For more information on this spectacular mission please visit NASA's Deep Impact website. Also, the Griffith Observatory has a nice page for finding the comet before impact happens.

The other notable event for July is the return to flight of the Space Shuttle. The shuttle has undergone some major upgrades and improvements since the Columbia disaster on February 1, 2003. NASA is viewing the next two flights of the shuttle as test flights. The shuttle Discovery is already sitting on the launch pad at the Kennedy Space Center in Florida ready for a launch. The launch was set for July 13th, but delayed until the 26th. Our hopes and prayers go out to the flight crew of STS-114 and NASA. Please visit the Return to Flight website to find out more about this important mission.

June 2005

Some things in the sky we can predict, like the motion of the planets. The planets move around the Sun in a very predictable way and we can calculate how the sky looks like thousands of years ago or thousands of years in the future. In a planetarium the projector actually can show you the sky of say 2000 years ago. Very interesting!

But sometimes there is a surprise, not with the planets but with comets. Every once in a while a new comet is discovered and if we're lucky it can be visible from Earth with the naked eye. Sometimes comets can be incredibly spectacular and covering half the sky with their tail. But of course that is very rare.

A comet is sometimes described as a dirty snowball; it is mostly ice but also some sand and dirt in there. But we do not truly know this is true because we have never landed on one to take a look! Well, next month, on the 4th of July this is going to change. NASA's Deep Impact will arrive by a comet called 9P/Tempel I, and release an 820 pound bullet that will slam into the comet at 23,000 miles per hour!

This will not destroy the comet at all, but by observing the comet before and after the impact we will learn a tremendous amount about what a comet is made of. For more information on this spectacular mission please visit Deep Impact's website.

Special Event

The special event for this month is the position of the three planets Mercury, Venus and Saturn. Starting around June 18 these three planets will seem to be dancing around each other, and on June 27 Mercury and Venus are less then a tenth of a degree apart! The timing could not be better because the best view is right after sunset. We have drawn three little images to give you an idea what to look for, but we're sure that if you step outside you will be able to find it by yourself. On June 18, Saturn Venus and Mercury will be approximately on one line about equal distance from each other. As you can see in the top image on the left Saturn is on 'top' venus in the 'middle' and Mercury at the 'bottom'. There are also two bright stars visible: Castor and Pollux. One easy way of telling the difference between a planet and a star is that a star twinkles and a planet does not. This would be a great test for that! On the following days the three planets will move closer to each other until eventually June 27 when Mercury and Venus almost overlap. They will be seperated by a mere 0.1 degree. (One degree is approximately the width of your index finger at armslength). Although Venus and Mercury are very close to each other, it is possible, albeit extremely rare, that they get so close to each other that your eye cannot separate them anymore. The result is then an incredibly bright twinkly 'star' that is sure to stop you when you see it. The last time this happened was in 1999, and the police got many phone calls from people who thought they saw a UFO!

May 2005

As you may have noticed, when you read about the planets of our Solar System some are referred to as 'He' and others as 'She'. Venus for example is feminine: Venus rises just after sunset she shines brightly. On the other hand Mars is masculine: Mars is slowly getting brighter as he comes closer to Earth. Of course there is nothing feminine or masculine about a planet, it is simply a result from the names we have assigned to the planets.

• Mercury:
  Mercury is the god of trade, profit and commerce.
  
  
• Venus:
  Venus is the Roman goddess of love and beauty, but originally she was the patroness of gardens and vineyards. Venus is a daughter of Jupiter, and Mars was one of her lovers.
  
  
• Mars:
  Mars is the god of war, and sadly one of the most prominent and worshipped gods. He started out though as the god of spring, growth in nature and fertility. But later he was associated with death and ultimately as the god of war. Mars is a son of Jupiter as well.
  
  
• Jupiter:
  Jupiter is the same god as Zeus and was the supreme god of the Romans. Another name for him is “dies pater” or “shining father”. He is the god of light and sky and protector of the state and its laws. He is Saturn’s son and brother of Neptune and Juno (who is also his wife).
  
  
• Saturn:
  Saturn is the Roman god of agriculture concerned with sowing of the seeds. Saturn is not only the father of Jupiter, but also of many others.
  
  
• Uranus:
  Uranus is the god of the sky. He was the first son of Gaia (the Earth) and also became her husband.
  
  
• Neptune:
  Neptune is the god of the sea, but was not very powerful. He is shown many similarities to the Greek god Poseidon.
  
  
• Pluto:
  Pluto is the god of the underworld and the judge of the dead. Pluto is a son of Saturn and he is a brother of Jupiter and Neptune.
  
  

There are many more gods in the Greek mythology, enough to also give all the moons of the planets names as well. Of course there are even more stories then names to all these mythological characters. Some of these stories are played out and depicted in the constellations. It can be great fun to learn and read about these stories, and they even can be used to generate interest in observing the sky or can be a help memorizing constellations. Be aware though that many of the stories are not suited for a younger audience because some of them are quite gruesome.

Special Event

Normally we do not write on this page on planets other then the ones that are visible to the naked eye. So we do not give advice on how to spot Uranus, Neptune or Pluto. This month however we would like to make an exception to that, because with a little luck you might be able to spot Uranus even with the naked eye if you know where to look.

In order to spot Uranus with the naked eye you will need to be at a very dark place. If you are in Austin with all the light pollution, you will need binoculars or a small telescope.

This month we will get the help from Mars, because Mars will be very close to Uranus, so if you can find Mars you will be able to find Uranus easily! On the 15th of May these two planets will be about one degree apart. One degree on the sky is about the width of your index finger at arms length. Uranus will be to the upper right from Mars. Good luck, and drop us a note if you are able to spot this planet!

The Space Shuttle Discovery was scheduled for a May 22nd launch date. This has been delayed until July due to additional concerns about the potential for damage to the heat shield by foam insulation or ice during launch. We are in no hurry except to see a spotless launch of the shuttle. Godspeed to Discovery when she does take us back into space.

April 2005

Astronomers of all kinds like to throw a party. This party doesn’t involve bright lights or a bunch of noise. This party requires some telescopes (the more, the merrier), a group of people who appreciate the stars and planets and a nice, quiet dark sky (the darker, the better).

This kind of party is called a Star Party. People from all walks of life and all ages are welcome at this party. People who know just a little or nothing about astronomy are very welcome here. People who know a lot about astronomy are at the Star Party and are very willing to teach others about the fun and science of astronomy. There are many telescopes you can look through, and if you have never seen Saturn through a telescope this is your perfect opportunity!

Austin's very own Austin Astronomical Society (AAS) is throwing just such a party during the month of April. We are telling you about it now, so you can put it on your calendar. Their star party is called the "CenTex Astronomy Weekend" this year and will be held during the weekend of April 15-16. Click here for more information on this fun event. Members of the Friends of the Austin Planetarium will be there as well to give a presentation and to answer any questions you might have. Come by and meet us! We’ll be glad to talk to you about what you can do to help bring a planetarium to Austin.

Special Event

There are two noteworthy events for this month; the opposition of Jupiter and the partial Solar eclipse that will be visible from the Central Texas area.

You know of course that all the planets revolve around the Sun, just like the Earth does. Each planet is at a different distance from the Sun, and therefore revolves slower or faster then the Earth, plus the circumference of each orbit is different as well. Needless to say, the Earth passes slower planets and also Earth is passed by planets that revolve faster. As a result sometimes it is very difficult to view a planet because it is so close to the Sun, and at other times the viewing is perfect.
That's the case this month for Jupiter. On the night of April 2-3 the Earth will be at the closest approach to this planet, we say then: "Jupiter is in opposition". As oppositions go though, this one is not the best. The orbits of planets are actually ellipses and not circles. So there are good (close) oppositions and 'bad' ones where the two ellipses (Earth and Jupiter in this case) happen to be at the greatest distance. Especially with Mars oppositions this is apparent because the orbit of Mars is very elongated. With Jupiter it is less so, but still noticeable for telescopic observations. Nevertheless Jupiter is spectacular, and if you wish to see Jupiter up close we invite you to come to the star party at Canyon of the Eagles on April 15 and/or 16.

The second event is a partial solar eclipse on April 8.

A schematic representation of a lunar Eclipse and a solar eclipse. The Earth is represented by the blue circle, the Moon is the orange circle and the Sun the yellow circle. This image is not to scale.

So now we have covered all the safety issues, it is time to talk about what will actually happen! On the 8th of April the Moon will travel between the Earth and the Sun, and for us in central Texas, partially obstruct the Sun. As a result we will see the Sun with a part missing! Unfortunately this gap is not very big and it will not get dark or anything (that only happens with a total solar eclipse), but it is still fun to watch. The event will start around 4:15 pm. and end at 6 pm.
If you would travel further south the gap would be bigger, and the eclipse will be total in Panama. Interestingly enough also the path of the moon is not circular, just like Jupiter's path around the Sun. Therefore the moon is sometimes a bit closer to us, and sometimes further away. During this eclipse the moon will be further then 'normal' and will be just smaller then the Sun. So although the eclipse is total, the moon will not completely cover the Sun but leave a fiery ring uncovered. This kind of eclipse is called an 'annular eclipse', and although it will get some darker, it is much less spectacular then a true solar eclipse.

March 2005

Astronomers of all kinds like to throw a party. This party doesn’t involve bright lights or a bunch of noise. This party requires some telescopes (the more, the merrier), a group of people who appreciate the stars and planets and a nice, quiet dark sky (the darker, the better).

This kind of party is called a Star Party. People from all walks of life and all ages are welcome at this party. People who know just a little or nothing about astronomy are very welcome here. People who know a lot about astronomy are at the Star Party and are very willing to teach others about the fun and science of astronomy.

Austin's very own Austin Astronomical Society (AAS) is throwing just such a party during the month of April. We are telling you about it now, so you can put it on your calendar. Their star party is called the "CenTex Astronomy Weekend" this year and will be held during the weekend of April 15-16. Click here for more information on this fun event. Members of the Friends of the Austin Planetarium will be there as well to give a presentation. Come by and meet us! We’ll be glad to talk to you about what you can do to help bring a planetarium to Austin.

Special Event

The Vernal equinox marks the beginning of spring in central Texas and the rest of the northern hemisphere. At this point, we know warmer weather is here to stay until late autumn. On both equinoxes (there is one for autumn as well) night and day are equal. In fact, the word equinox comes from Latin, meaning ‘equal night.’ After the vernal equinox, days become longer and nights shorter all the way until the summer solstice in late June. Equivalently, nights become longer with the advent of the Autumnal equinox. These events are opposite for the southern hemisphere.

A representation of the ecliptic and the apparent path of the sun

Of course you know that the sun rises in the East and sets in the West, but not only sun does that also the moon rises in the East and sets in the west. In addition the planets do exactly the same! Almost all the objects from our solar system make the same apparent path through the sky: from East to West. The reason for this is that our solar system is flat, all the planets rotate in a disk (or a plane) around the sun and all the planets rotate in the same direction. The path that the planets and the moon follow is called the ecliptic.

As you may know, the earth is tilted on its axis (about 23.5°) in relation to its path around the sun. The angle of tilt can be seen on most globe atlases of earth. This tilt defines how big the Arctic and Antarctic Circle is at each end of our planet. Each region is tilted away from the sun for six months and tilted toward it the following six months. This, of course, is the reason each polar region has half year of light (i.e. the ‘Land of the Midnight Sun’) and a half year of darkness. The vernal equinox marks the first day the sun shines at the North Pole, and the beginning of six months of darkness at the South Pole.

February 2005

Happy first birthday Spirit and Opportunity!
It has been already a year since the two rovers landed on Mars. Originally NASA had as goal to have these rovers operational for 90 days, so clearly by hitting the 365 day mark, this mission has been a huge success, and is still ongoing.
As we all know, space missions are very difficult and sometimes it is impossible to predict what will happen. A good example was the Huygens probe: will it land on surface or water? Taken the fact that we cannot look through the atmosphere of Titan the probe had to be ready for anything! As it turned out it was neither rock nor water: Huygens landed in mud! The same holds true of course for the two little rovers on Mars. Each day is a new adventure, and each day things can go wrong. Something can break without warning, or a rover might meet an obstacle that it cannot handle.
But thankfully nothing of the sort has happened and both rovers are still healthy and driving every day around the surface of Mars. For more information on the Mars mission please check out the Mars Rover website. There are tons of things to explore, pictures and movies to watch and even receive free materials from NASA. They have also an enormous amount of material available for children and educators.

January 2005

In January 1610, Galileo Galilei (1564-1642) used a telescope to observe our Moon and discovered that Jupiter had moons of its own – almost 400 years ago. Galileo was an Italian mathematician and philosopher. He heard of the telescope, a new invention, several months earlier. Even though Galileo did not invent the telescope, and he was not the first person to point a telescope at the heavens, his eventual contributions made people change the way they think about astronomy, mathematics and the sciences.

The telescope was apparently invented by a Dutch eyeglass maker, Hans Lippershey (1570-1619). He took lenses he had made and placed two of them at opposite ends of a tube. There is a legend that his children actually did this and showed this discovery to their dad. (We will talk about the invention of the telescope in more detail in a future Astro News.) Galileo took what he knew about the telescope and worked on improving lens grinding techniques, thus making a more powerful telescope. The first telescope he built could magnify images 3 times their actual size. By January 1610, he had a telescope that could magnify things 20 fold.

Galileo thought he was seeing “fixed stars” near Jupiter with his first effort of pointing his telescope at that planet. After several observations, he noticed there were four of these objects. More importantly, he became convinced that these “stars” were actually orbiting Jupiter. Galileo knew the importance of this discovery (if he was right) and published his findings in a short book he called Sidereus Nuncius or "The Starry Messenger."

Back in Galileo’s day, a person could be imprisoned or executed for stating the universe was not Earth-centered. To state that we lived in a Sun-centered, or heliocentric, universe was considered subversive and extreme by the Catholic Church. This almost sounds silly in today’s world of space travel, computers and the sciences, but in Galileo’s world, a person’s life depended on such things. About 100 years earlier, Polish astronomer Nicolai Copernicus (1473-1543), the father of the heliocentric universe, refused to publish his ideas from fear of being persecuted by the Church and his peers.

Galileo made many careful observations of the four Jovian moons. He described these in detail in Sidereus Nuncius. Galileo saw this as further proof that we lived in a heliocentric universe. Even though these thoughts eventually got him into trouble with the Catholic Church), Galileo continued his observations. In 1616, he was warned by Pope Paul V (who was a lifelong friend of Galileo’s) not to continue his teachings of a Sun-centered system. By 1633, he was placed under house arrest for the remainder of his life. His past friendship with the pope is probably the only thing that kept Galileo from being executed. His findings and the advances he made in telescope building changed the field of astronomy in many deep, meaningful ways. We still refer to Jupiter’s four big moons as the Galilean moons, in his honor.

Special Event

This Month's special event is an interesting event, but you will need at least a small telescope or good binoculars. (If you use binoculars make sure that you have a stand, or a good place for the binoculars to rest on). Jupiter's four largest moons are easy to spot: 4 bright spots very close by the planet. The names of these 4 moons are: Ganymede, Europa, Io and Callisto. There are a lot of people tracking these moons just for fun and follow how they orbit the largest member of our Solar System. With a telescope you can follow them and observe all kinds of interesting events: elcipses and shadows of the moons crossing on the face of Jupiter. This actually happens on the 9th this month when Europa casts a shadow on Jupiter, but to see that you really will need a telescope. The other (more easily observed) event for this month is, that three of the moons (only Ganymede is missing) will be 'bunched' together on one side of Jupiter. Can you spot them?

January 2005

Special Event

On January 14, the Huygens probe will enter the atmosphere of Saturn’s large moon Titan and attempt a soft landing on the surface. This probe separated from the Cassini spacecraft on December 24th while they were both on a collision course with Titan. Cassini changed its course on December 27th, to keep it from striking Titan. Huygens will descend through Titan’s atmosphere for two and a half hours. The probe will ‘taste’ the atmosphere as he descends to Titan’s surface. Then he will transmit the collected data back to Cassini, then relay it to Earth. Titan’s atmosphere is mostly nitrogen and methane. Huygens should reveal any other gases that are present in small amounts. These trace gases can give us a more complete picture of how Titan formed and why it has an atmosphere.

For more information on the Cassini-Huygens mission please visit the home page of the mission to Saturn and Titan.

December 2004

On December 25, the Cassini mission that arrived at Saturn a couple of months ago, will release the Huygens probe which will land on the moon Titan; Saturn's largest moon. This will be one of the Cassini mission milestones.

Titan was discovered in 1655, by Dutch astronomer Christiaan Huygens (April 14, 1629 - July 8, 1695). Christiaan came from an important Dutch family. His father was the famed (by the Dutch at least) Constantijn Huygens who was a philosopher but most importantly a diplomat. Christiaan received a private education at home by tutors until he was 16 years old, after which he studied Law and Mathematics at the University of Leiden.

At a certain point, Christiaan turned his attention to lens grinding and polishing and soon discovered a way to improve this process. He was therefore able to build superior telescopes that could resolve objects in the heavens not seen before. When he set out to study Saturn he indeed spotted the first moon: Titan. He was also able to make a detailed study on the shape of Saturn's rings.

Another very important invention Huygens made was the pendulum clock. Making observations and scientific research requires precise timekeeping, which was unavailable at the time. The pendulum clock was a major improvement, making it finally possible to measure longitude on board ships traveling the globe.

Just like Cassini, Huygens was a man that had a great influence on our history and both made incredible inventions. What a great way to honor these two great men by naming the Cassini-Huygens mission after them.

At this point we still do not know what the Huygens probe will find on Titan. We do not even know if it will land on solid surface or if it will splash down in some liquid. The Huygens probe has been built to be able to do both and to take pictures of its surroundings. Unfortunately the probe will not live very long at the most a couple of hours before it stops sending data. For more information on the Cassini-Huygens mission please visit the home page of the mission to Saturn and Titan.

Special Event

As you can see on the calendar; this December is quite a busy month. We won't detail everything that happens this month, but we will highlight some of the more remarkable events: the occultation of Jupiter on December the 7th, and the alignment of the planets.

Last October we had a spectacular Lunar Eclipse, where the moon travels through the Earth's shadow, or said differently: where the Earth traveled between the Sun and the Moon. If we would have been on the moon we would have seen a solar eclipse! This time something similar happens, where the Moon will stand between the Earth and Jupiter. From Earth, the moon will obscure Jupiter and some time later Jupiter will reappear from behind the Moon's limb. This reappearance should be quite spectacular because the moon will not be full and Jupiter will reappear from the dark crescent of the Moon. You will have to get up early for this though because the moon won't rise till 2 am right around the same time the 'show' will start for observers in Central Texas. Less then half an hour later Jupiter will be visible again.

Less spectacular, but still noteworthy is the alignment of all the major Planets. As you can read in this month 'The Planets' section (see above) all planets are visible and easily spotted later in the month. From the 10th through the 13th while not all of them are visible yet, they do appear in the sky in the same order as their respective distances from the Sun! The order is of course: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and even Pluto appears in the right spot. For Uranus and Neptune you will need a telescope. Mercury & Pluto are too close to the Sun and as a result they are impossible to see.

Although scientifically lineups like these are meaningless, they are very rare. A lineup like this will not happen again for another 400 years!

November 2004

The top Image is the outside of the Eise Eisinga museum in Franeker, The Netherlands. The lower picture is a portion of the machinery to keep the planetarium going. (images courtesy Eise Eisinga Planetarium)

Last month we observed a lunar eclipse, and this month we have the chance to see the conjunction of Venus and Jupiter. These two events have something in common: they both can cause fear with people that do not understand what is happening.

A very good example is the conjunction of four planets in the year 1774. Some people were afraid that the planets would actually run into each other, which would lead to the end of the world! This viewpoint was even published by a newspaper in the Netherlands.

Thankfully, a local wool-comber in the Dutch town of Franeker thought this was so outrageous that he decided to set these people straight. He built a scale model of the solar system (a planetarium, in other words) right in his living room. His name was Eise Eisinga. He built the entire contraption from wood; all of it by hand. Eventually, he indeed had a working scale model in his living room. It adequately showed the movement of the planets and moon. He was able to show and explain to people how our solar system works. By this wonderful visual resource he created, he was able to demonstrate to others that we do not need to be afraid that the planets will ever run into each other.

During the construction of all this, his wife had to put up with a lot. Their house was rather small, and the only place where the required pendulum could go was right in the middle of where their bed was at. After some re-design efforts, Eise was able to move the clockwork mechanism off to one side of their bedroom. This allowed the bedroom to be useable again and probably went a long way to making amends with his wife.

Another amazing thing about Eise’s planetarium is that it is still working to this day! The entire house has been turned into a museum. It is now the world’s oldest working planetarium! If you ever visit the Netherlands, it is definitely worth to take a trip to Franeker and see Eise’s Planetarium.

Special Event

This month's special events are the Venus/Jupiter conjunction and the Leonid meteor shower.

The morning of November 5th should be a real treat. For months Jupiter and Venus have been traveling towards each other (that is called their appulse), and now they will reach conjunction: their closest apparent approach. The dazzling pair of Venus and Jupiter will rise about three hours before the Sun. The two should be a little further apart than your finger held at arm’s length. Try viewing with a pair of binoculars or a telescope with a low power lens. You should be able to see both of these beauties together through the eyepiece. But also with the naked eye, this will appear quite spectacular. The two will actually appear closest (reach conjunction) when they are still below the horizon on the evening of the 4th.

The Leonid meteor shower reaches its peak on the morning of the 17th. They seem to originate from the constellation Leo, hence their name. Their true source is the comet Temple-Tuttle, which orbits the Sun about every 33 years. When a comet gets close to the sun, millions of tiny particles are thrown from the comet, thus creating a big path of these particles. The Earth’s orbit happens to pass through a small part of this path. When one of these particles (usually no bigger than a small grain of sand) enters the Earth’s atmosphere, it burns up. Because the Leonids are moving at such a high speed in relation to Earth, a number of these meteors leave a long vapor trail. Comet Temple-Tuttle was nearest the Sun in 1998. The following four years were quite spectacular for viewing the Leonids. People were seeing thousands of meteors within an hour’s time. This year we should expect anywhere from 15 – 100 meteors per hour, which is still quite impressive.

Talking about the comet Temple-Tuttle; NASA has planned a mission to this comet, and not just to take pictures! The mission is called ‘Deep Impact’ and they actually plan to slam a spacecraft into the comet to see what will happen to it, and to learn more about the structure of comets. For more information on Deep Impact, you can visit the official Deep Impact website. NASA hopes to launch Deep Impact in January 2005.

October 2004

Long ago, people thought that an eclipse of the Sun or the Moon had a specific meaning. Of course, no one understood exactly what was happening when the Sun suddenly disappeared, and people were fearful, thinking that it was caused by an angry god.

The first person to successfully predict a solar eclipse was the Greek philosopher Thales, who predicted the solar eclipse of May 585 BC! This is quite amazing, because Thales did not have a computer or calculator more than 2500 years ago.

Today, of course, we understand how the planets and their moons move and interact in our Solar System, and we can predict and calculate any eclipse with great precision.

Solar eclipses occur in patterns or 'Eclipse Seasons', which are periods when an eclipse (or many eclipses) are possible. This is the way Astronomers can calculate that it is possible to have up to 5 (!) solar eclipses in one year, as happened in 1935.

Here is another interesting fact: if there is a total lunar eclipse, this always is accompanied by a solar eclipse! This October is no exception: although invisible from Austin, people in Alaska will see a partial solar eclipse this month.

Special Event

This month's special events are the Orionids but the real showpiece is the
total lunar Eclipse.

The Orionids are, just like the Perseids in August, an annual meteor shower. Although the Orionids are normally less spectacular then the Perseids, there is always a chance of seeing something amazing. The Orionids seem to emanate from just north of the constellation of Orion. The maximum activity of probably around 15 shooting stars per hour will occur after midnight around October 22-nd. For further instructions on observing the Orionids, please check the information on the Perseids, which is described in the August edition of AstroNews.

On October 27, we're in for a treat! The only spoiler could be clouds, but other than that, a total lunar eclipse is even clearly visible from downtown. There are two kinds of eclipses: a solar eclipse, where the Moon is in between the Sun and the Earth, and a lunar eclipse, where the Earth is in between the Sun and the Moon (see graphic below).

A schematic representation of a lunar Eclipse and a solar eclipse. The Earth is represented by the blue circle, the Moon is the orange circle and the Sun the yellow circle. This image is not to scale.

Solar eclipses are very rare and incredibly spectacular if you are at the right place at the right time. They are so rare, that we will have to wait until the year 2017 until we see one again over the continental United States. But when you have the opportunity, you truly should make an effort to see it, because it is an unforgettable experience. However, although spectacular, they are very short-lived: in the matter of 2 or 3 minutes the Sun becomes visible again and the effect is ruined.

Lunar eclipses however, are more common. There are several reasons for this; firstly, the earth is much bigger and therefore has a larger shadow for the Moon to travel through. Secondly, with a solar eclipse, the shadow must pass over you in order to see the eclipse, and then only the observer can see this. But for a lunar eclipse you see the effect of earth's shadow on the Moon, so everyone who can see the Moon can see the eclipse! Because of all this, a lunar eclipse also lasts much longer than a solar eclipse; more than an hour instead of minutes.

Around 8 p.m., we can start to see the first effects when the Moon starts to travel into the Earth's shadow. The start of the eclipse is when the Moon reaches the penumbra (partial shadow), which is the light-gray colored region in the graphic above. You will even be able to see that the shadow on the Moon is curved and not a straight line, because the earth is a sphere. The second phase is when the Moon reaches the umbra or full shadow region. When the whole Moon is in the umbra, we have totality. The Moon will be a wonderful spooky reddish color for over an hour; what a nice treat right before Halloween!. Then the Moon will touch the penumbra again, and slowly travel out of the Earth's shadow completely, until we have 'just' a normal full moon again at about 12:30 a.m.

Observing the eclipse is very easy: just take a chair to your yard and enjoy. The Moon will still be rather low on the horizon at 7 p.m., but will gradually move higher. Simple binoculars or a small telescope may enhance the experience but are not needed. Because we are looking at the Moon, observing is completely safe. You do not have to take any precautions as would be needed if viewing a solar eclipse. Just don't forget to blink when you are awed by Mother Nature!

September 2004

Of course you know that the sun rises in the East and sets in the West, but not only sun does that also the moon rises in the East and sets in the west. In addition the planets do exactly the same! Almost all the objects from our solar system make the same apparent path through the sky: from East to West. The reason for this is that our solar system is flat, all the planets rotate in a disk (or a plane) around the sun and all the planets rotate in the same direction.

A representation of the ecliptic and the apparent path of the sun

The path that the planets and the moon follow is called the ecliptic. The moon nearly follows this path as well, but strays above and below it in the time (almost a month) it takes to go around the earth once. During this time, the moon crosses the ecliptic twice. From the Greek word for ‘failure to show up’ an eclipse happens when the sun, moon and earth form a straight line as the moon crosses the ecliptic. If the order of the line is sun-moon-earth, we have an eclipse of the sun – or solar eclipse. This is when the moon’s shadow is on the earth. If the sun-earth-moon line up, we have a lunar eclipse – the earth’s shadow is cast onto the moon. With either of these situations, a full or partial shadow is present. If the alignment is exact, then we have a total eclipse.

As you may know, the earth is tilted on its axis (about 23.5°) in relation to its path around the sun. The angle of tilt can be seen on most globe atlases of earth. This tilt defines how big the Arctic and Antarctic Circle is at each end of our planet. Each region is tilted away from the sun for six months and tilted toward it the following six months. This, of course, is the reason each polar region has half year of light (i.e. the ‘Land of the Midnight Sun’) and a half year of darkness. The autumnal equinox marks the first day the sun shines at the South Pole, and the beginning of six months of darkness at the North Pole.

August, 2004

As you have undoubtedly heard the current mission to Saturn is called The Cassini-Huygens Mission. The name Cassini is in honor of the Italian/French astronomer Giavanni Dominico Cassini. He was born June 8, 1625 in Nice, Italy and died at the respectable age of 87 (in 1712 in Paris, France).

As was more common in those days, Cassini was much more than just an astronomer. He wrote papers on hydraulic engineering, was an inspector of water and waterways, and was also the superintendent of the improvements to a castle! We remember him mostly for the discoveries he made as an astronomer.

Cassini, together with his colleague Jean Richer, was the first to actually calculate the distance to the planet Mars. This told them something about the size of our solar system. This was a very important discovery! Back then nobody knew how far away from Earth (or each other) the planets were, let alone the size of the Universe. Likewise, in Cassini's day, there were discussions about whether the Earth was flat and whether or not the Earth rotated. He was the first to observe and measure rotation of other planets. Because all the other planets rotated, Cassini speculated that the Earth rotates as well. Why would the Earth be any different?

He also discovered four moons around Saturn (Tethys, Dione, Rhea and Iapetus), (co-) discovered Jupiter's red spot and was the first to observe the large gap in the rings of Saturn, which we call the Cassini division. Wow, what an amazing person he must have been!

For more information on the Cassini-Huygens mission to Saturn go to the NASA Mission home page.

Special Event

This month's special events are related: the Autumnal Equinox and the Harvest Moon.

The Autumnal equinox marks the beginning of fall in central Texas and the rest of the northern hemisphere. At this point we can officially begin anticipating cooler weather :-). On both equinoxes (there is one for spring as well) night and day are equal. In fact, the word equinox comes from Latin, meaning ‘equal night.’ After the autumnal equinox, nights become longer and days become shorter all the way until the winter solstice in December. Equivalently, days become longer with the advent of the Vernal (spring) equinox. These events are opposite for the southern hemisphere.

The Harvest Moon is just the name we give to the full moon closest to the autumnal equinox. As with every full moon, the harvest moon rises right at sunset. During the year – on average – the moon rises 50 minutes later each evening. The harvest moon rises only about 25 minutes earlier each night for several nights, thus keeping after twilight darkness at bay for at least an extra week while the moon is fat. This was important to farmers gathering crops in the many centuries before electricity. These days it helps us forget – for a little while – that the days are truly getting shorter. The reason the Harvest Moon rises just 25 minutes later each night is because the moon’s path is closest to the ecliptic (see the Did You Know section below) at this time of year.

August 2004

Special Event

This month's special event is the Perseid Meteor shower. Peak viewing is on the night of August 12th into the morning of the 13th. The Perseids are remnants from the comet Swift-Tuttle and are named for the constellation Perseus. Just like train tracks seem to come together at the horizon, 'shooting stars' of a meteor shower also seem to originate from a single point. In this case, they seem to emanate from the stars that make up the constellation Perseus.

Meteors are small pieces of rock and dirt varying in size from tiny dust particles to sand grains with an occasional pebble thrown into the mix. When a comet travels through our solar system, the sun heats the comet causing some evaporation. The comet leaves behind a dust trail. When the earth's orbit travels through such a trail, the dust hits our atmosphere at a great speed causing it to burn up. Often, these meteor showers are recurrent and predictable to a certain degree. The Perseid meteor shower is an annual event but the intensity of this year's shower (how many shooting stars per hour) is uncertain. Under a dark sky, 60 - 100 per hour is typical for this shower. However, there are indications this year's Perseids might be a lot better (say 300 an hour) or spectacular like a 1000 or more per hour!

The moon cooperates nicely this year for the Perseid Meteor shower - by being mostly absent. If the sky is clear and you are away from city lights, conditions should be ideal for observing. The darker the spot you can find the better. Also, make certain you have a clear view of (especially) the North-North Eastern sky. Unfortunately, for most, the best time to observe meteor showers is very early in the morning with the peak around 3 a.m. We might get lucky this year and see a terrific show at around 11 p.m.

Good luck viewing - and if you see a falling star, please wish for a planetarium!

For more information on the Perseid Meteor shower you can read the article from Sky & Telescope magazine.