Exam 2, Version A Answer Key

[The final version was lost on my laptop, and the exam on-line does not have the letters for the answers. In addition, a couple of the questions were changed. But, for study purposes, this version should suffice as there were not that many significant changes from this one to the one that was given. I've given most of the answers below--but may not have finished the sentences.] YOU CANNOT USE THESE ANSWERS WITH THE ACTUAL EXAMS, only the one linked here.

1.  material from a coronal mass ejection
2. convection; granulation
3. in a very small volume at center
4. expand and hence cool
5. mass of helium nucleus is smaller
6. Sirius
7. Rigil Kent
8. Achernar
9. Achernar
10. Achernar

11. HRD is not where stars are located
12. B
13. E.
14. A
15. D
16. C
17. color
18. how much energy per secone
19. star must be quite large
20. wavelength would be greater

21. most hydrogen atoms are ionized
22. most of electrons are in ground state
23. they are not gravitationally bound
24. masses
25. we cannot resolve the individual stars
26. all of the above
27. luminosity
28. app. mag, temp., or app. mag., temp, and luminosity (should have read luminosity class)
29. we don't measure the star's redshift for the distances
30. emission nebulae shine because of excited gas; dark are dust

31. electrons in hydrogen gas have been excited to upper energy levels
32. particles in the dust are reflecting light from star
33. at a wavelength of 21 cm
34.  all of the answers were accepted
35.  in giant molecular clouds
36. force of gravity
37. gpe
38. thermal energy
39. conservation of ang momentum
40. mass energy

41. mass
42. precise locations
43. stars just slightly redder are just evolving off main sequence
44. the relative distances
45. B is older
46. B is farther away