midterm3_5_sol

# midterm3_5_sol - ASTR 100 Midterm 3 Version 5 Solutions...

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ASTR 100 Midterm 3 Version 5 Solutions April 19, 2006 Multiple Choice, 2 pts each. 1. B 6. D 11. C 16. B 21. C 2. B 7. A 12. C 17. D 22. A 3. B 8. B 13. C 18. B 23. B 4. C 9. B 14. C 19. A 24. A 5. C 10. B 15. C 20. D 25. C Short Answer, 10 pts each. 1. Imagine that the Sun does NOT rotate on it axis. What major aspect of the Sun would be different? Explain why. If the Sun did not rotate on its axis, the biggest change (from how the Sun is today) is that it would not have a sunspot cycle. That’s because sunspots would not form. The Sun’s magnetic field is the cause of sunspots. If the Sun did not rotate, it would still have a magnetic field (it would probably be much weaker). However, the magnetic field lines would not wrap up around the Sun because of differential rotation. That means that the magnetic field lines would not get stressed and stretched, and would not bend sharply through the surface of the Sun. The sharp bends in the magnetic field lines are the ultimate cause of sunspots, so sunspots would not form. Thus, there could not be a sunspot cycle, or any associated solar activity, such as prominences, flares, or coronal mass ejections. 2. In the space below, sketch an H-R diagram. Make sure to include labels on each axis, along with the direction of increasing value, as well as the major patterns that are usually seen on the diagram. Now add the following to your diagram: Mark and label a point for star A , which is the main-sequence star with the shortest lifetime. Mark and label a point for star B , which is a red giant . Mark and label two points for stars C and D , which have the same luminosities , but different temperatures .

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