Finding the Planets

Today, we take a more observational approach to our astronomy lesson which will require you to go outside tonight and look at the stars. If  you've taken a look at the sky lately, you might have noticed a few extra bright objects up there. These bright objects are not really large stars, they are actually the planets in our solar system! Three of the planets (Venus, Mars and Jupiter) are visible just after sunset right now (assuming skies are clear where you are!) To find the planets, start by looking west. You should see two very bright objects in a straight line fairly low in the sky, brighter than any other stars around them. These are Venus (brightest one) and Jupiter! Once you've found them, turn around and look east. There should be another bright object in the sky that has a distinct red hue to it. That is Mars! Below are some images from Sky & Telescope magazine showing you where the planets are in relation to other stars and the moon. (Even though they say April 2nd they are about right for any day this week)

If you happen to have a telescope, or an observatory near by, take a look at these planets. If the night is very clear, you might be able to see the four Galilean moons of Jupiter or even the polar ice caps on Mars! It's really a spectacular sight!

Jupiter's Ice Moon Europa: Part 2

We discussed Europa's icy surface and possible sub-surface ocean last week. Some images that Galileo sent back showed bumpy features on Europa's surface, almost like blisters. These features (shown below)  look similar to places on Earth where glaciers sit on top of undersea volcanoes. Basically, these underwater vents heat the water above them which melts the overlaying ice. Since these volcanoes are not active all the time, there are periods where the water can re-freeze on the surface. This re-freezing does not leave a smooth sheet, but rather a chaotic frozen pattern, much like the pattern seen on Europa. So what does this all mean? It suggests that there is some sort of internal heating mechanism within the moon, and therefore a subsurface ocean! The depth of this ocean, and the thickness of the ice sheet is still unknown, but further observations and hopefully future missions will enlighten us on Europa's mysterious structure.

 

Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain. Image Credit: Paul Schenk/NASA

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