Interstellar Matter

Answers

INTERSTELLAR MATTER

1. nebulae (singular = nebula)

2. 10,000

3. diffuse or emission, BIRTH, dust, EMISSION

4. reflection, dust, SCATTERED

5. planetary, white dwarf, EMISSION

6. dark, BIRTH

7. birth

8. radio

9. H I, H II

10. NEAR THE PLANE OF THE GALAXY, FAINTER, redder, iron, carbon,
silicates, ices

11. GAS, DOES NOT

THE MILKY WAY GALAXY

12. Milky Way, milk

13. pinwheel, spiral, hub (bulge or nucleus)

14. pancake (flattened), hub (bulge or nucleus), DUST

15. 100,000, globular

16. Milky Way, center, 30,000

17. metal, 2

18. II, I

19.                                    Population I                     Population II

Color                                   bluer                                 redder
Age                                     newer                                 older
Metal Content                     higher >2%                     lower <2%
Interstellar Gas and Dust     abundant                             scarce

20. trillion, halo, HIGHEST, black hole

21. circular

GALAXIES IN GENERAL

22. galaxies

23. BILLIONS, Andromeda, Magellanic Clouds

24. Hubble

25. spiral

26. ellipticals

27. irregulars

28. 20, Local Group, FOUND

29. Virgo, THOUSANDS

30. ABSORPTION, Seyfert

31. radio

32. active, black holes

33. quasars

THE UNIVERSE

34. universe

35. cosmology

36. Olbers, Olbers's
    a. The universe is infinite: No, the universe is finite. It does not contain an infinite
    number of stars.
    b. The expanding universe: Because the universe is so large and getting larger by the
    second, there has not been enough time to fill it completely with the light from every
    star which it contains.
    c. The red shift: Displaces (weakens) much of the visible radiation of stars to longer
    wavelengths, particularly into the infrared, which the eye cannot see. But the sky is
    dark in most wavelengths, including the infrared. Thus the red shift by itself cannot
    explain Olbers' Paradox.
    d. Dust: Absorbs and scatters some of the radiation before it reaches us, but again
    this is not an explanation for Olbers' Paradox because the dust must reradiate the
    energy in a longer wavelength.

37. big bang

38. Hubble, receding

39. expanding, about 50

40. age, OLDER,

41. 13, DIFFICULT

42. time, EARLIER

43. All quasars are far away. There are none close to us. This means that quasars were
    once part of a younger universe and that quasars no longer exist or have evolved into
    other objects.

44. density, oscillating

45. expand forever, open, open

46. steady state