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Unformatted text preview: ASTR 100 Midterm 3 Version 3 Solutions April 19, 2006 Multiple Choice, 2 pts each. 1. A 6. C 11. A 16. A 21. C 2. A 7. B 12. A 17. C 22. C 3. D 8. D 13. A 18. B 23. A 4. C 9. A 14. B 19. B 24. B 5. C 10. C 15. A 20. C 25. D 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. Thats because sunspots would not form. The Suns 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. Below this question is a figure with three spectra. The wavelength scale at the bottom is correct for each spectrum. The spectrum labeled B was observed in a laboratory on Earth. The spectra labeled A and C were observed from stars. Examine the spectra carefully and answer the following questions: (a) Which star is moving the fastest, and how do you know? (b) Is the fastest-moving star moving toward the Earth or away from the Earth? How do you know?...
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- Spring '06