Assignment #6

Assignment 6: Extra-Solar Planetary Systems and Kepler's 3rd Law of Planetary Motion

Due: in class on February 21, 2008

1. Visit the Marcy website, http://exoplanets.org/planets.shtml and find the orbital periods and sizes of the orbits of the planets for 55 Cnc (55 Cancri), the system with 5 planets. Tabulate the properties.

2. Show that Kepler's 3rd Law of Planetary Motion holds for the planetary system chosen. To do so, express the orbital periods as multiples of the orbital period of the planet with the shortest period, and express the orbital sizes as multiples of the orbital size of the planet with the shortest orbital period, and then apply Kepler's 3rd Law of Planetary Motion.

Would Kepler's 3rd Law of Planetary Motion, P2 = a3, have worked out if you had chosen to express P and a in terms of the properties of the Earth? Verify your answer.