All problems are from the text, Universe (7th edition) by Freedman & Kaufmann.

* Extra credit.

Extras: Part of the assignent is to complete these questions:

A. Repeat the exercise posed in 4-35 for Ceres, the largest known asteroid. Aphelion of Ceres is 2.99 AU; perihelion is 2.55 AU.

B. The most spectacular comet in recent times was Hale-Bopp, with a closest approach to the sun of 0.9 AU. It won't be back soon, having an orbital period of 2,500 years. What is its aphelion?

C. Look at the surface gravities of the planets in Appendix 2. These are given in units of Earth's familiar g = 9.8 m/s/s. Use the data in Appendix 3 to compute the surface gravity (in g) on Phobos, Callisto, and Titan.

- Note that Phobos is not spherical, so the answer depends on which axis you choose. Pick one and give a reason for your choice.

Be sure to show your work. A simple "Yes" does not constitute a complete answer. You must write in complete sentences and show all mathematical computations to receive full credit. Your homework must be legible for us to grade it - please be neat!