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Exam 15: Surveying the Stars

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Question 61

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If the distance between us and a star is doubled,with everything else remaining the same,the luminosity

A) is decreased by a factor of four,and the apparent brightness is decreased by a factor of four.
B) is decreased by a factor of two,and the apparent brightness is decreased by a factor of two.
C) remains the same,but the apparent brightness is decreased by a factor of two.
D) remains the same,but the apparent brightness is decreased by a factor of four.
E) is decreased by a factor of four,but the apparent brightness remains the same.

F) A) and D)
G) C) and D)

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Question 62

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The sketch below 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) A
B) B
C) C
D) D
E) E

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

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Question 63

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The following questions refer to the sketch of the H-R diagram below.Please choose the best answer in each case,i.e. ,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 includes stars that are burning elements besides hydrogen in their cores?

Careful measurements reveal that a star maintains a steady apparent brightness at most times,except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours.The most likely explanation is that

Refer to the choices in the table for the following questions. -Which star has the greatest luminosity?

The sketch below 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?

The sketch below 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?

The following questions refer to the sketch of the H-R diagram below.Please choose the best answer in each case,i.e. ,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 stars that are hot and very bright?

Stars on the upper left of the H-R diagram are longer lived than those on the lower right.

The apparent brightness of a star depends only on its luminosity.

Which of the following persons reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars?

What are the standard units for luminosity?

Process of Science: How do scientists estimate stellar luminosities?

The star Vega has an absolute magnitude of about 4 and an apparent magnitude of about 0.Based on the definitions of absolute and apparent magnitude,we can conclude that

Spectral type,surface temperature,and color all describe the same basic characteristic of a star.

All stars are born with the same basic composition,yet stars can look quite different from one another.Which two factors primarily determine the characteristics of a star?

Which of the following is true about low-mass stars compared to high-mass stars?

Which of the following statements about an open cluster is true?

The sketch below 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 are cool and dim?

On the main sequence,stars obtain their energy