ROBERTS REVIEW I PHYSICS 1060
1. The nearest star is over one parsec distant.
a. True
b. False
2. The proper motion of a star is its true velocity through space.
a. True
b. False
3. The "solar constant" refers to the observation that the Sun's brightness does not ever change.
a. True
b. False
4. The 21-centimeter emission of hydrogen is the result of the electron making a transition from its very highest energy level to the next level down.
a. True
b. False
5. All else being equal, the hotter a star is, the brighter it will be.
a. True
b. False
6. Solar neutrinos, observed on Earth, originate in the solar corona.
a. True
b. False
7. Emissions from molecules are the only means we have for determining the conditions inside a molecular cloud.
a. True
b. False
8. Spectral type M stars are cooler than type O.
a. True
b. False
9. A spectral type A main sequence star is brighter than a type B main sequence star.
a. True
b. False
10. The fusion of hydrogen is difficult to produce because four hydrogen atoms must collide simultaneously in order to fuse into helium.
a. True
b. False
11. The temperature inside a molecular cloud is typically colder than other interstellar matter.
a. True
b. False
12. Interstellar matter is distributed very evenly through the galaxy.
a. True
b. False
13. When describing the properties of stars, solar units of mass and radius are often used.
a. True
b. False
14. One parsec is a little over 200,000 A.U.
a. True
b. False
15. The Sun's density is about the same as Saturn's.
a. True
b. False
16. Heavy elements are not seen in interstellar gas because they go into making interstellar dust.
a. True
b. False
17. Starlight sometimes is polarized as it passes through the interstellar medium because dust particles are spherical.
a. True
b. False
18. Almost all stars have radii between about 0.1 and 10 times the radius of the Sun.
a. True
b. False
19. Star A and star B have the same apparent magnitude. Star A is twice as distant as star B. Therefore, star A has twice the luminosity as star B.
a. True
b. False
20. Emission nebulae glow because they absorb ultraviolet light from nearby hot stars.
a. True
b. False
21. There are absorption lines seen in the Sun's spectrum corresponding to 83 different elements.
a. True
b. False
22. A type G star is hotter than a type K.
a. True
b. False
23. A type B star is hotter than a type A.
a. True
b. False
24. The chromosphere is faint because of its low density.
a. True
b. False
25. Molecular clouds are much warmer than typical interstellar gas clouds.
a. True
b. False
26. Dark dust clouds radiate mainly in the radio portion of the electromagnetic spectrum.
a. True
b. False
27. A G2 star is cooler than a G3.
a. True
b. False
28. Hydrogen lines are weak in both very hot and very cool stars.
a. True
b. False
29. Atomic nuclei are held together by the strong force.
a. True
b. False
30. A magnitude 2 star is 100 times as bright as a magnitude 12 star.
a. True
b. False
31. Why couldn't you stand on the Sun's surface?
a. You could stand on the surface.
b. The Sun doesn't have a solid surface.
c. The Sun's surface is too highly magnetized for anything to survive there.
d. You could stand on it, if a sufficiently protective spacesuit could be designed.
32. Which of the following best describes the size and distance relationship of our Sun and the nearest star?
a. Two beachballs separated by 100 city blocks.
b. Two grains of sand separated by 100 light years.
c. Two golfballs separated by 100 kilometers.
d. Two baseballs separated by 100 yards.
33. Why are dark dust clouds largely misnamed?
a. They contain much more gas than dust.
b. The appearance of a cloud is an illusion; dust is scattered very evenly throughout the Galaxy.
c. Dust clouds are not dark but emit significant amounts of visible light. They just look dark compared to the bright stars.
d. all of the above
e. none of the above
34. How would sunspots appear if you could magically remove them from the Sun?
a. Because sunspots are dark spots, they would be invisible against the blackness of space.
b. They would shine brightly.
c. They would not appear any differently than on the surface of the Sun.
d. They would shine only with reflected sunlight.
35. Of the many complex molecules found in interstellar space, most are based on which element?
a. Hydrogen.
b. Silicon.
c. Oxygen.
d. Carbon.
36. What effect does dust have on visible light passing through it?
a. It dims and reddens it.
b. It completely blocks all visible light from passing through.
c. All light is turned bluish in color.
d. It makes the light coming from stars appear to twinkle.
37. What is the average temperature of interstellar gas and dust?
a. 3K
b. 100 K
c. 1,000 K
d. 10,000 K
e. 0 K
38. The light we see from the Sun comes from which layer?
a. chromosphere
b. photosphere
c. corona
d. convective zone
39. Which of the following spectral types is the hottest?
a. G2.
b. G3.
c. G4.
d. G5.
40. The density of interstellar dust is extremely low but it can block starlight because:
a. most of this matter is found surrounding stars and not dispersed in the regions between the stars.
b. interstellar dust particles are equal in size to wavelengths of visible light.
c. there is about 100 times more gas than there is dust.
d. interstellar dust particles have elongated shapes.
41. What is the meaning of the "solar constant"?
a. the regularity of the sunspot cycle
b. the surface features of the Sun never change
c. the size of the Sun never changes
d. the solar energy reaching Earth per unit area per unit time
e. the constancy of the proton-proton cycle that produces the energy of the Sun
42. Spectra of stars often show narrow absorption lines from interstellar matter. What type of interstellar matter produces these?
a. dust
b. neutral gas
c. ionized gas
d. molecules
43. Interstellar absorption lines are narrow primarily because:
a. there is very little interstellar matter
b. molecules always produce narrow absorption lines
c. most of the matter is ionized
d. the matter is at a low temperature
44. A nearby star has a parallax of 0.2 arc seconds. What is its distance?
a. 0.1 pc
b. 0.2 pc
c. 0.5 pc
d. 2 pc
e. 5 pc
45. What information does 21-centimeter radiation provide about the gas cloud that emitted it?
a. radial velocity
b. density
c. temperature
d. all of the above
e. none of the above
46. When the chromosphere can be seen during a solar eclipse, what is its color?
a. white
b. blue
c. yellow
d. green
e. red
47. What is the net result of the proton-proton chain?
a. 2 heliums are fused into 1 carbon, 1 neutrino + energy
b. 4 hydrogens are fused into 1 helium, 2 neutrinos + energy
c. 2 hydrogens and 1 helium are fused into 1 carbon + energy
d. 2 protons and 2 neutrons are fused into 1 carbon + energy
48. The most common molecule in a molecular cloud is:
a. H2
b. CO
c. H2O
d. HCN
e. NH3
49. Compared to the size of the Sun, in what range of sizes are most stars found?
a. 0.1 to 1.0 solar radii
b. 0.5 to 5.0 solar radii
c. 1 to 100 solar radii
d. 0.01 to 100 solar radii
e. 1 to 10 solar radii
50. What is the size of a typical white dwarf?
a. 0.01 solar radii
b. 0.5 solar radii
c. 0.1 solar radii
d. 1.0 solar radii
e. 5 solar radii
51. What is the size of a typical red giant?
a. 100 solar radii
b. 0.5 solar radii
c. 1000 solar radii
d. 1.0 solar radii
e. 5 solar radii
52. What physical property of a star does the spectral type measure?
a. luminosity
b. temperature
c. radius
d. mass
e. composition
53. The component of our Galaxy that has most hindered astronomers' efforts to understand the overall nature and structure of the Milky Way Galaxy is the ______.
54. The HR diagram is a plot of ______.
a. luminosity versus mass
b. temperature versus radius
c. luminosity versus temperature
d. radius versus mass
e. temperature versus mass
55. In the HR diagram, what is the approximate position of the Sun?
a. bottom left
b. top right
c. top left
d. bottom right
e. center
56. What are the characteristics of an open cluster of stars?
a. old age and tens of thousands of stars
b. no main sequence stars and up to a million stars
c. a few hundred, mostly main sequence, stars
d. large size and tens of thousands of stars
57. M stars are ______in color.
58. The ______may be the repository of much of the heavy elements returned to the interstellar medium via supernovae explosions.
59. The failure to detect sufficient numbers of ______coming from the Sun has raised serious questions about our understanding of the solar interior.
60. The ______is the outermost, hottest part of the Sun's atmosphere.
61. Most interstellar molecules that have been observed have been detected in the ______region of the electromagnetic spectrum.
62. The method of spectroscopic parallax is limited to stars for which both a ______and a measure of apparent brightness can be obtained.
63. Absorption lines in the solar spectrum are formed in the ______.
64. The observable surface of the Sun is a thin layer in which the solar material becomes suddenly much more ______as we look into the Sun.
65. If two stars are emitting the same amount of light, the closer star will appear to be ______.
66. Energy transport in stars can occur by large-scale motions of the stellar material in regions called _____.
67. The spectra of two stars show they are the same type of star; if one appears 5 magnitudes brighter than the other, the distance ratio of the two stars must be ______.
68. The spectral type of a star tells us the star's ______.
69. Briefly describe the properties of the interstellar dust that exists in the interstellar medium.
70. The magnitude scale is defined such that a magnitude difference of 5 corresponds to a luminosity ratio of ______.
71. The only particle we can detect directly from a stellar interior is the ______.
72. The tenuous, hot outer atmosphere of the Sun is the ______.
73. In what ways do the stars of our Galaxy interact with the interstellar medium?
74. Binary stars yield the basic information on stellar ______.
75. Explain how "forbidden" lines appear in spectra of emission nebulae.
76. The measurement of the solar ______suggests that we do not completely understand either the interior conditions of the Sun or the theory of elementary particle physics.
77. Solar energy is produced by the ______of light weight hydrogen into the heavier atom helium.
78. The strongest lines present in the spectra of A stars are absorption lines of ______.
79. The ______varies dramatically in shape over the solar cycle.
80. Stellar masses are determined directly by observation of the orbits and periods of ______stars.
81. The ______is a spectroscopic classification based on the shapes of stellar absorption features; broader absorption lines imply higher gas pressure in the stellar photosphere and hence a smaller and fainter star at a given temperature.
82. ______is a photometric method of determining a star's surface temperature.
83. What happens in the radiative zone?
84. What is the significance of the solar neutrino experiment?
85. If we know the temperature of an object, its luminosity may be inferred if we also know its ____.
86. The following stars all have nearly the same apparent brightness in the sky. Locate them in a Hertzsprung-Russell Diagram. Sirius, a type A, Main Sequence star; Rigel, a blue supergiant; Betelgeuse, an M-type (red) supergiant; Procyon, a type F, Main Sequence star; alpha Centauri, a type G, Main Sequence star.
Of these stars,
a) which is coolest?
b) which is closest?
c) which is largest?
d) which is representative of the most common type of star?
e) which is the longest lived?
87. Two stars have apparent magnitudes of 0 and 5. If both stars are 117 parsecs away, which star is intrinsically brighter and by what factor is it brighter than the other?
88. Draw a Hertzsprung-Russell Diagram and answer the following questions:
a) In which region are the white dwarfs located?
b) Which group of stars are the red supergiants?
c) Which is the region of the most common type of star?
d) Which stars are the most massive Main Sequence stars?
e) What is the location of the Sun?
f) In which region are the least massive stars found?
g) In which region are the red giant stars?
h) Where are stars like Sirius, Vega, and Procyon?
i) Which is the region of the largest stars?
j) Which is the region of the smallest stars?
89. State the mnemonic for the seven spectral classes from hottest to coolest.
90. What must one observe to obtain the mass of a star a) that is in a binary system? b) For one that is not in a binary system?