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46. The greater the distance to a galaxy, the greater a redshift in its in general the spectral classification scheme based on
spectral lines. This is known as temperature and stellar spectra.
a. Doppler’s law. 9. What is the Hertzsprung-Russell diagram? What is the
b. Cepheid’s law. significance of the diagram?
c. Hubble’s law.
10. What is meant by the main sequence of the H-R diagram? What one
d. Kepler’s law.
thing determines where a star is plotted on the main sequence?
47. Evidence that points to the existence of black holes was provided by
11. Describe in general the life history of a star with an average
a. Mauna Lao Observatory.
mass such as the Sun.
b. Hubble Space Telescope.
12. What is a nova? What is a supernova?
c. radio astronomy.
d. LGM. 13. Describe the theoretical physical circumstances that lead
to the creation of (a) a white dwarf star, (b) a red giant,
48. The name of our galaxy is the
(c) a neutron star, (d) a black hole, and (e) a supernova.
a. solar system.
b. main sequence. 14. Describe the two forces that keep a star in a balanced, stable condition
c. Milky Way. while it is on the main sequence. Explain how these forces are able
d. Polaris. to stay balanced for a period of billions of years or longer.
49. What is the obstacle to finding extraterrestrial life? 15. What is the source of all the elements in the universe that are
a. Money more massive than helium but less massive than iron? What is
b. Number of stars the source of all the elements in the universe that are more
c. Distance and time massive than iron?
d. Language 16. Why must the internal temperature of a star be hotter for
50. Outer space is mostly helium fusion reactions than for hydrogen fusion reactions?
a. galaxies. 17. When does a protostar become a star? Explain.
b. stars. 18. What is a red giant star? Explain the conditions that lead to the
c. planets. formation of a red giant. How can a red giant become brighter
d. empty space. than it was as a main sequence star if it now has a lower
51. Initial evidence that supports the big bang theory of the creation surface temperature?
of the universe came from 19. Why is an average star like the Sun unable to have carbon
a. experiments conducted by shuttle astronauts. fusion reactions in its core?
b. unmanned space probes. 20. If the universe is expanding, are the galaxies becoming larger?
c. redshift calculations by Edwin Hubble. Explain.
d. data from the Hubble Space Telescope.
21. What is the evidence that supports a big bang theory of the
Answers universe?
1. c 2. c 3. c 4. b 5. a 6. d 7. d 8. a 9. a 10. b 11. c 12. d 13. a 14. b 15. d
16. c 17. b 18. c 19. c 20. c 21. b 22. a 23. d 24. b 25. a 26. c 27. a 28. c FOR FURTHER ANALYSIS
29. a 30. a 31. a 32. d 33. c 34. b 35. c 36. c 37. a 38. c 39. a 40. b 41. a
42. d 43. a 44. c 45. d 46. c 47. b 48. c 49. c 50. d 51. c
1. A star is 517 light-years from Earth. During what event in
history did the light now arriving at Earth leave the star?
QUESTIONS FOR THOUGHT 2. What are the significant differences between the life and eventual
fate of a massive star and an average-sized star such as the Sun?
1. Would you ever observe the Sun to move along the celestial 3. Analyze when apparent magnitude is a better scale of star
meridian? Explain. brightness and when absolute magnitude is a better scale of star
2. What is a light-year and how is it defined? brightness.
3. Why are astronomical distances not measured with standard 4. What is the significance of the Hertzsprung-Russell diagram?
referent units of distance such as kilometers or miles? 5. The Milky Way galaxy is a huge, flattened cloud of spiral arms
4. Explain why a protostar heats up internally as it gravitationally radiating out from the center. Describe several ideas that
contracts. explain why it has this shape. Identify which idea you favor and
explain why.
5. Describe in general the structure and interior density, pressure,
and temperature conditions of an average star such as the Sun.
6. Which size of star has the longest life span: a star 60 times more INVITATION TO INQUIRY
massive than the Sun, one just as massive as the Sun, or a star that
has a mass of one-twenty-fifth that of the Sun? Explain.
It Keeps Going, and Going, and . . .
7. What is the difference between apparent magnitude and
absolute magnitude? Pioneer 10 was the first space probe to visit an outer planet of our so-
8. What does the color of a star indicate about the surface lar system. It was launched March 2, 1972, and it successfully visited
temperature of the star? What is the relationship between the Jupiter on June 13, 1983. After transmitting information and relatively
temperature of a star and the spectrum of the star? Describe close-up pictures of Jupiter, Pioneer 10 continued on its trajectory,
eventually becoming the first space probe to leave the solar system. Since

14-23 CHAPTER 14 The Universe 373