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Based on the definition of apparent brightness, which units are appropriate for its measurement?


A) Watts per square meter
B) Watts
C) Joules
D) Newtons

E) All of the above
F) B) and C)

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The faintest visible stars to the naked eye have an apparent magnitude of about 6

A) True
B) False

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The approximate main-sequence lifetime of a star of spectral type O is ________.


A) 3 million years
B) 10,000 years
C) 300 million years
D) 10 billion years

E) A) and D)
F) C) and D)

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The spectral sequence sorts stars according to


A) mass.
B) surface temperature.
C) luminosity.
D) core temperature.
E) radius.

F) A) and E)
G) A) and D)

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On an H-R diagram, stellar radii ________.


A) increase diagonally from the lower left to the upper right
B) are greatest in the lower left and least in the upper right
C) decrease from left to right
D) are impossible to determine

E) A) and D)
F) A) and C)

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The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e) ; note that (a) represents the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group represents stars that have no ongoing nuclear fusion?


A) a
B) b
C) c
D) d
E) e

F) A) and E)
G) A) and C)

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The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e) ; note that (a) represents the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group represents the most common type of stars?


A) b
B) c
C) d
D) e

E) C) and D)
F) None of the above

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Which of the following statements about apparent and absolute magnitudes is true?


A) The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared.
B) A star with an apparent magnitude of 1 appears brighter than a star with an apparent magnitude of 2.
C) The absolute magnitude of a star is another measure of its luminosity.
D) A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth.
E) All of the above are true.

F) B) and C)
G) All of the above

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The Earth is about 150 million km from the Sun, and the apparent brightness of the Sun in our sky is about 1,300 watts per square meter. Determine the apparent brightness we would measure for the Sun if we were located five times the earth's distance from the Sun.

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The Sun would appear 1/25 time...

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On a Hertzsprung-Russell diagram, where would you find stars that are cool and luminous?


A) upper right
B) lower right
C) upper left
D) lower left

E) A) and B)
F) None of the above

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Two stars, Betty and Wilma, are both on the main sequence. Betty is more luminous than Wilma. Which one has a hotter surface temperature? Which one is more massive? Which one is bigger? If they both formed at the same time, which one will evolve off the main sequence first?

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Since they are both on the main sequence...

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Which of the following comparisons between low-mass stars and high-mass stars is true?


A) Low-mass stars are cooler and less luminous than high-mass stars.
B) Low-mass stars are hotter and more luminous than high-mass stars.
C) Low-mass stars are cooler but more luminous than high-mass stars.
D) Low-mass stars are hotter but less luminous than high-mass stars.
E) Low-mass stars have the same temperature and luminosity as high-mass stars.

F) A) and B)
G) A) and E)

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Confusing Terminology in Science: Scientists' love of jargon and acronyms often confounds the public and makes it impossible for them to read scientific literature. Use the example of spectral types introduced in this chapter (i.e. the Sun is a "G2" star) as a case study in jargon. What is the historical origin of the spectral types? Why are the letters in a confusing, non-alphabetical order? Why do you think astronomers persist in using spectral types? Do you think astronomers should drop this notation, and, if so, what should replace it?

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The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is 10 billion years old?


A) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is 10 billion years old? A) B) C) D)
B) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is 10 billion years old? A) B) C) D)
C) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is 10 billion years old? A) B) C) D)
D) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is 10 billion years old? A) B) C) D)

E) B) and D)
F) A) and C)

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The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is the youngest?


A) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is the youngest? A) B) C) D)
B) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is the youngest? A) B) C) D)
C) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is the youngest? A) B) C) D)
D) The following questions refer to the representations below of H-R diagrams for different clusters of stars. In each diagram, the dotted lines locate the position of the Sun. -Which cluster is the youngest? A) B) C) D)

E) A) and B)
F) A) and C)

Correct Answer

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The sketch above shows groups of stars on the H-R diagram, labeled (a) through (e) ; note that (a) represents the entire main sequence while (c) and (d) represent only small parts of the main sequence. Which group represents stars with the longest main-sequence lifetimes?


A) a
B) b
C) c
D) d
E) e

F) B) and C)
G) A) and B)

Correct Answer

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The following questions refer to the sketch of the H-R diagram below. Choose the best answer in each case. Note that choice (a) refers to the entire main sequence, while (c) and (d) refer to only small parts of the main sequence. If choice (c) or (d) offers a better answer to a particular question than (a) , use the best choice. You may use the same choice more than once. The following questions refer to the sketch of the H-R diagram below. Choose the best answer in each case. Note that choice (a) refers to the entire main sequence, while (c) and (d) refer to only small parts of the main sequence. If choice (c) or (d) offers a better answer to a particular question than (a) , use the best choice. You may use the same choice more than once. -Which group represents hydrogen-burning stars with the shortest lifetimes? -Which group represents hydrogen-burning stars with the shortest lifetimes?

Correct Answer

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Which of the following luminosity classes refers to stars on the main sequence?


A) I
B) II
C) III
D) IV
E) V

F) B) and D)
G) C) and E)

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A star with a parallax angle of 1/20 arcsecond is ________.


A) 20 parsecs away
B) 20 light-years away
C) 1/20 parsec away
D) 10 parsecs away

E) B) and D)
F) A) and D)

Correct Answer

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Which star cluster is the youngest star cluster? The one where the brightest main sequence stars are . . .


A) O stars.
B) A stars.
C) G stars.
D) M stars.
E) B stars.

F) C) and E)
G) B) and C)

Correct Answer

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