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