ASTR 1110H – Homework #2

Fall 2009 – Dr. Magnani

1. Explain Kepler’s 3 Laws in your own words.

2. What is the connection between Kepler’s Second Law and the Law of Conservation of Angular Momentum?

3. What is the problem, astronomically speaking, with Kepler’s Three Laws? (Hint: Let’s say you discover a planet going around a nearby star. Can you use Kepler’s Laws to describe the behavior of the planet’s orbit?)

4. What is the problem, philosophically, with Kepler’s Three Laws?

5. Copernicus resurrected the heliocentric model of the Solar System. Describe how the motion of Venus and Mercury is now explained (in contrast to the geocentric system). Explain how retrograde motion of the outer planets is now explained.

6. Where in its orbit is a planet moving most quickly? Where most slowly?

7. If you discover a new planet orbiting the Sun at a distance of 46 AU, how long does it take to orbit the Sun?

8. If a planet takes 2 weeks to orbit the Sun, how close to the Sun is it?

9. Imagine a comet with an aphelion distance of 50 AU and an orbital eccentricity of 0.1. How long does this comet take to orbit the Sun?

10. If an object in the Kuiper Belt has a perihelion distance of 40 AU and an aphelion distance of 65 AU, how long does it take to orbit the Sun? What is the eccentricity of the orbit?