Syzygy!

Syzygy of the Sun, Moon and Earth

Ok admit it… you really want to know what syzygy means don't you? No I didn't make it up, it actually has something to do with astronomy! When the sun, Earth and the moon or another planet all happen to line up in a straight line we call that a syzygy (pronounced "siz-i-jee"). To be honest I had never heard this before until I stumbled upon a website of random astronomy facts, and this was one of them! Syzygys (syzygies?) occur during a lunar or  solar eclipse, and when Mercury or Venus crosses in front of the sun from Earth's point of view. Sometimes syzygy is used to describe a strange formation of the planets, such as when they are all on the same side of the sun.  According to Google it's also the name of a few restaurants, a Japanese band, and a type of god in the Gnosticism belief system. I think next time something astronomically cool happens I'm going to give it a fun name and see if it sticks….

Image credit: NASA

Star Formation

 

 

Ever wonder how stars form? Astronomers have been thinking about that for quite a while, and are pretty sure they have a good idea about how it works. Stars form out of giants clouds of gas and dust in space. The tiny particles bump into each other until they stick and form a large ball of gas. This protostar, as astronomers call it, gravitationally attracts the cloud of gas surrounding it and increases in size until most of the gas has fallen onto the star. What's left is a big ball of gas surrounded by a disk of dust particles which accretes (falls onto) the star. Some of the dust in this circumstellar disk will stick together to form rocks, and a few may even grow big enough to be planets! After about 10 Million years (yes million!) the star will accrete most of the dust and become a "young adult" star, or Zero Age Main Sequence star. The star is now big enough and hot enough to burn Hydrogen in its core (left side of diagram). If the star doesn't accrete enough gas and dust to become large enough to burn hydrogen, it becomes a brown dwarf (right side of diagram). Most of the stars that you see in the night sky are average main sequence  stars of various sizes and ages.

Ring Around The.... Planets?

Open a new tab in your internet browser (yes, right now). Go to Google and pull up an image of Saturn (I don't care that you know what it looks like, just do it). Remember that picture, and look up a picture of Jupiter, Uranus and Neptune as well. Now if I start singing the song "One of these things is not like the other…" what would your answer be?...... The answer I was going for was Saturn! What's so different about Saturn? Well as you saw from the picture, Saturn has a beautiful ring structure and the other planets don’t….. Wrong! Believe it or not, all of the gas giant planets have rings! (Now if you didn't actually go to Google before, I bet you are now just to see if you can find a wiki page on ringed planets to see if I'm right.) 

 

Saturn's ring structure is very bright and prominent because it is thick and made mostly of ice which reflects light. The rings around Jupiter, Uranus, and Neptune are much thinner and are mostly made of rocks. Pictures of each planets rings are shown above. There's a big black spot over Neptune because Neptune is so bright compared to its rings that the planet's light needed to be blocked out so the rings were visible . Now when someone refers to Saturn as the ringed planet you can say "actually, all the gas giants have rings… but I know which one you mean."

Image credits: NASA/Voyager/J. Rayner/NSFCAM/IRTF

Week of Moons: Titan

Silly me forgot to post the final week of moons update on Friday, as blogspot was down Friday morning. So here is the final Week of Moons post about Titan. It ties in nicely with today's post about Cassini-Huygens.

 

Titan, the largest moon of Saturn, is one of my favorites. Why? Well take a look at the infrared picture above (bottom left) and tell me what it looks like….. Earth! Titan is very much like Earth was way back when it was just a baby, about 4 billion years ago.  It's about half the size of Earth and has a dense nitrogen atmosphere. It's the only moon in our solar system that has a thick atmosphere, and the only object to have flowing liquid and lakes on it! Unfortunately these lakes are not water lakes, but methane lakes (too toxic for humans to swim in!) There are also volcanoes which spew out  water and methane (cryovolcanism), suggesting that there might be a layer of liquid water underneath Titan's crust! Astronomers think that Titan may be the best place to look for life in our solar system, as it is so similar to Earth. The Huygens Lander discovered in 2005 that the surface of Titan contains carbon compounds, further supporting the idea of possible life! Now we don't expect to find an alien civilization walking around, but we may find bacteria or other organisms who've adapted to the conditions and are living either on the surface or in the methane lakes. NASA and ESA are planning robotic missions to land on and study Titan, but no official announcements on when this will occur have been made. I guess we will just have to wait and see!

Image Credit: NASA/JPL/Cassini-Huygens

Cassini-Huygens Mission

The Cassini Huygens mission launched in 1997 with the purpose of studying Saturn and it's Earth like moon Titan. The spacecraft reached Saturn in 2004 where Cassini entered orbit around Saturn. Huygens landed on Titan about one year later. If you've ever looked at Saturn through a telescope it's absolutely spectacular. On a good night you can clearly see the rings and even some of the moons! It almost looks like someone put a scrapbooking sticker of Saturn at the end of the telescope, it's that clear. Cassini giving us an up close and personal look at the planets and it's moons;the image above being one of them. A 2 minute video of images Cassini sent back to Earth is the feature of today's Astronomy Picture of the Day. Check it out here

Image credit:

NASA/JPL/Space Science Institute

Week of Moons: Triton

Today we have a guest post by Laura Arnold about Neptune's moon Triton!

The largest moon of Neptune, and the 7th largest moon in the solar system, has a peculiar orbit. It orbits opposite the rotation of Neptune. Moons are theorized to form in the same way solar systems are, from a rotating flattened disk of gas and dust. And the fact that all of the planets orbit the Sun in the same direction as the sun rotates supports this theory. Scientists think that Triton's backward orbit indicates that it once orbited the Sun and was captured by Neptune when they came close to each other. In order for a massive body to enter into orbit around Neptune and not just whizz right by it would have to lose a lot orbital energy, or angular momentum. One theory states, that if Triton had a moon itself or was in a planetary binary system, Triton could be captured if the excess orbital energy had been carried off by its satellite which with all this energy would be ejected from orbit around Triton and Neptune

 

 Voyager 2 returned pictures of Triton in 1989, revealing an icy surface with very few impact craters. The surface of Triton smooth in some places and crinkled, like the skin of a cantaloupe, in other places. Because of the lack of cratering, it is thought that Triton's got a face-lift around 10-100 million years ago. This resurfacing could be done if ice in Triton's interior was heated due to tidal interactions with Neptune or heat from radioactive decay. This would provide for a liquid ocean under the icy surface of Triton, similar to Jupiter's moon Europa and Saturn's moon Enceladus. If pressure built up enough, ice volcanoes (cryovolcanism) could form spewing liquid, likely water mixed with ammonia and methane, onto Triton's dreadfully cold surface (colder than -382 F) which would then freeze. Voyager 2 saw two active geysers on Triton which spewed nitrogen gas as high as 8 km into the air. The energy powering these geysers is thought to come from sunlight, as these arose around the point on Triton which receives the most sunlight (though this is still about 1 thousandth of what Earth receives.)

 Image credit: NASA/JPL/USGS

Week of Moons: Did Man Really Land On The Moon?

Believe it or not, this  is a very controversial question: Did man really step foot on the moon? I'm sure many of you that were alive to  see Buzz Aldrin and Neil Armstrong set foot on the moon in 1969 would go "of course we did!" But there are still a lot of skeptics out their that think this was all a big hoax. Well I wasn't around back then to see it, but I really think we did land on the moon! Here's some proof....

One way to prove that we landed on the moon is to take a picture of the landing site. Above is an image taken by the Lunar Reconnaissance Orbiter, a satellite that's orbiting the moon and taking pictures, of the Apollo 11 landing site and astronaut foot prints. It sure looks like we landed and walked there! The Astronauts also left a reflector on the moon, much like one that you have on your bicycle. With a very high powered laser you can actually bounce the laser beam off this reflector, and trust me astronomers have tried this out and succeeded. I mean seriously, who would pass up the  opportunity to play with a high powered laser? (See episode 63 of The Big Bang Theory. Point proven.) The reflectors are also used to accurately measure the distance between Earth and the moon and do tests of Einstein's theory of general relativity.

Now you may ask why haven't we gone  back? And my short answer to that is money and ethics. Sure it's cool to send astronauts into space, but If we can do better science with cheaper robotic equipment and don't have to put lives in danger, then why would we send man to the moon again? Don't get me wrong, I'm very much for manned space missions, but in our society we tend to do things the cheapest and safest way we can. And that means, sadly, no more manned missions to the moon.

Want to see more proof that the moon landing was real? Check out Mythbusters episode #104

Image credit: NASA/LRO