Astronomy 120: Fall 2008

Homework 4: Due in September 26/29 recitation

Name ___________________________ Section _______

Q1:
(This is an essay question from an old Astro 120 exam... good practice!)

In 1543, Copernicus published his book that promoted the idea that the Sun, not the Earth, was the center of our Solar System. Decades later, Tycho Brahe and then Johannes Kepler became two very important figures in the "Copernican Revolution" yet their views of our solar system could not have been more different. Tycho firmly believed in a geocentric solar system while Kepler finally revealed the "modern" view of the heliocentric scheme.

In a less-than-one-page essay, discuss the changing view of our Solar System, focusing on the roles of Tycho Brahe and Johannes Kepler. In your essay, begin by explaining why Tycho rejected the Copernican system. Pick up the story with Kepler, emphasizing his connection with Tycho, and how he improved upon the Copernican model. In your essay, you should address the following questions: What different asumptions did Kepler make? What did he have to work with that Copernicus did not? How did that help?  
 
 
Q2:
In 1804, astronomers discovered a new "planet" that orbited the Sun with a period of 4.36 years. Using Kepler's laws (and showing your work) compute the size of the semimajor axis of this object's orbit around the Sun.  

Between the orbits what two of the classical planets does this object orbit the Sun?  
 
 
Q3:
Kepler's three laws describe orbits of bodies around our Sun. At about the same time that Kepler was determining his 3 laws, Galileo discovered the 4 large moons of Jupiter. Given what we now know, would Kepler's laws also apply to the moons of Jupter as they orbit the planet? What parts would be different (if any) and what parts would be the same?