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Exam 11: Surveying the Stars

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Question 21

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A star of spectral type B with a mass of 10 times the mass of the Sun lives approximately how long on the main sequence?

A) 1,000 years
B) 10,000 years
C) 10 million years
D) 1 billion years
E) 10 billion years

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Question 22

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What is the approximate age of a star cluster where the brightest main sequence stars are G stars?

A) 10 million years
B) 100 billion years
C) 10 billion years

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Question 23

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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 one-third of the earth's distance from the Sun.

Star A has an apparent magnitude of 3, and Star B has an apparent magnitude of 5. Which star is brighter in our sky?

Explain why stars more massive than the Sun live shorter main sequence lives than stars less massive than the Sun, despite having more fuel available for nuclear reactions.

Our Sun is a star of spectral type ________.

Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?

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 are extremely bright and emit most of their radiation as ultraviolet light?

Which of the following statements about open clusters is true?

The age of stars in a cluster can be determined by

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 includes stars that are burning helium in their cores?

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 of the largest radii?

We can measure the parallax of most stars in our galaxy.

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

Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?

Which of the following statements about spectral types of stars is not generally true?

If Star A is closer to us than Star B, then Star A's parallax angle is ________.

Two stars both lie on the main sequence. Star X is spectral type A, while Star Y is spectral type G. Star X must be more massive than Star Y.

Our Sun, An Average Star: Often in science it is helpful to talk about a representative example of the objects or phenomena being studied. However, you must always keep in mind that the average case is not always representative. For example, our Sun is often described as an "average" star in the Milky Way. In what sense is this statement true? In what sense is this statement seriously misleading? Do you think it is useful to characterize the stars in the Milky Way by simply citing our "average" Sun?

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 ________.