29:52 Homework Set #4

Assigned: October 31, 2004

Due: November 8, 2004

Here’s a Halloween scare for you! Another homework set. If you have questions about these problems, contact me for clarification or help. You should also communicate with your classmates via the bulletin board.

1. What physical principle is responsible for the fact that the Jovian planets and their satellites are much colder than the Earth?

2. In the lecture I said that the mass of Jupiter is 318 times that of the Earth. Describe a sort of observation which could be done to prove this statement. I am not asking for physics equations, but I do want adescription of the physical principle you are invoking, as well as the observation.

3. We say that Jupiter is a large sphere of gas, rather than a solid object like the Earth. Why is it that when you look at Jupiter through a telescope (or look at the pictures of it in your textbook), you see a sharp edge to the planet? Use information presented in figures in the lecture notes or the textbook.

4. How thick is the layer in the atmosphere of Jupiter that would have temperatures in the range you have experienced in your lifetime? Notice that temperatures in astronomy are usually expressed in degrees Kelvin, which is the number of degrees above absolute zero. 273 degrees Kelvin corresponds to the freezing point of water (32 degrees Fahrenheit). Each degree Kelvin hotter or cooler than 273 K is 1 degree Centigrade above or below the freezing point of water.

5. In class and in the textbook, the claim was made that the interior of Jupiter and Saturn consists of a substance called liquid metallic hydrogen , that has been produced on Earth only under the most extreme conditions in physics laboratories. What is it about the interior of Jupiter and Saturn that causes these conditions to occur naturally? Why doesn’t this substance occur on the surface of the Earth?

6. On the web page for Sky and Telescope magazine, http://skyandtelescope.com there is an item under “News” for October 28, with the title “Titan, a world apart”. In it, they report that very recent observations of the surface of Titan by the Cassini spacecraft showed no impact craters of the sort we see on the Moon. What does this tell us about Titan?

7. How does the Earth’s moon compare in size to the Galilean satellites of Jupiter? In other words, which of the Galilean satellites are larger in diameter, and which ones are smaller? Use numerical data in your answer.

8. The major reason for current interest in the Galilean satellite Europa comes from the strong possibility that there is an ocean under the surface of this moon. Describe an observation of Europa which suggests that this ocean exists.