Astronomy 305G, Fall 2009

Homework 1. Due date: September 1 (Tu), please turn in at beginning of class period.

1. What is meant with a "habitable planet"? Does that mean it surely has life on it?

2. As the distance between a planet and the Sun increases, the planet will receive less and less Sun light. As a result, we might expect the temperature of the planet to systematically decrease with increasing distance from the Sun. Hence, let us test the hypothesis that the temperature of a planet only depends on its distance from the Sun. To investigate this for the planets in the solar system, look up the average distance from the sun and the average temperatures of the planets (you can include Pluto here). You should try to find an "average temperature" for each planet (the text book might help), for a fair comparison you should not confuse one planet's temperature on the night side with another planets day-side temperature. List the source(s) of where you found the temperatures.

Now make a graph that plots the average temperature of the planets on the vertical axis versus their distance from the Sun on the horizontal axis of your graph. Is our hypothesis correct? Comment on the results. What are some other factors that affect the average temperature on a planet?