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!!!