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.