AST 307 · Introductory Astronomy

Fall 2003

AST 307
Homework #5
Due Friday October 10
 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.
 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.
