# Homework 7. The Rotation of the Sun

 Name: ________________________ Due 10/17 ID Number: ________________________

Here are six images of the Sun taken on six days in September 2005. A very large sunspot can be seen crossing the Sun's disk -- in fact, this spot was so large that it could be seen without a telescope!

 [http://www.bbso.njit.edu/cgi-bin/LatestImages]
 1. On the circle at right, plot the position of the sunspot on each successive day. Then, draw a line across the disk indicating the Sun's equator, and show which direction the Sun is rotating.

2. Now, using the spot positions you plotted in step #1, measure the distance between the spot's position on 09/11/05 and its position on 09/16/05. Divide your result by the diameter of the circle. This gives you the fraction of the Sun's diameter the spot moved between 09/11/05 and 09/16/05.

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3. The Sun's circumference C is related to its diameter D by C =  D. Using your result for step #2, what fraction of the Sun's circumference did the spot move?

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4. Finally, given that approximately 5 days elapsed between 09/11/05 and 09/16/05, how long would it take the spot to make one complete circle around the Sun and return to its original position? This is the Sun's rotation period.

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