AST 307 · Introductory Astronomy Fall 2003

AST 307
Homework #5
Due Friday October 10

1. Our textbook says that the motion of the Sun caused by the gravitational pull of Jupiter is 12 km/s. Go through the numbers to show that this is right (or wrong). You already know the ratio of the mass of Jupiter to the mass of the Sun from homework set #3, or you can calculate it from numbers in your book. You can look up the orbital radius and period of Jupiter in your book.
a) From these numbers, calculate the speed of Jupiter in its orbit.
b) Calculate the radius of the little circle the Sun goes around because of the gravitational pull of Jupiter. (Newton's 3rd law requires that both Jupiter and the Sun orbit around their center of mass.)
c) Given that the time for the Sun to go around this little circle is the same as the orbital period of Jupiter, calculate the speed of the Sun's motion.

2. Either from your book, or better yet from a web search, find out something about a spacecraft that is scheduled to study one of the planets in the next year or two. Give a short description of what it is supposed to do.

7 October 2003
Astronomy Program · The University of Texas at Austin · Austin, Texas 78712
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