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30 Cards in this Set

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Approximately, what basic composition are all stars born with?


a) half hydrogen, half helium, no more than 2 percent heavier elements


b) one-quarter hydrogen, three-quarters helium, no more than 2 percent heavier elements


c) three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements


d) 90 percent hydrogen, 10 percent helium, no more than 1 percent heavier elements


e) 98 percent hydrogen, 2 percent helium

c. three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements

Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?


a) luminosity they are formed with


b) location where they are formed


c) mass they are formed with


d) color they are formed with


e) time they are formed

c. mass they are formed with

What are the standard units for luminosity?


a) watts per second


b) kilograms


c) joules


d) watts


e) Newtons

d. watts

A star's luminosity is the


a) total amount of light that the star radiates each second.


b) total amount of light that the star will radiate over its entire lifetime.


c) lifetime of the star.


d) apparent brightness of the star in our sky.


e) surface temperature of the star.

a. total amount of light that the star radiates each second

What are the standard units for apparent brightness?


a) watts per second


b) watts per square meter


c) watts


d) joules


e) Newtons

b. watts per square meter

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


a) remains the same, but 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) is decreased by a factor of four, and 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.

a. remains the same, but the apparent brightness is decreased by a factor of four

Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star?


a) they are identical for most stars.


b) All stars put out most of their light in the visible range of the spectrum.


c) Astronomers are lazy.


d) Most stars do not put out light in other ranges of the spectrum.


e) In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.

e. In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths.

Suppose you measure the parallax angle for a particular star to be 0.1 arc-second. The distance to this star is


a) 0.1 parsec.


b) 0.1 light-year.


c) 10 parsecs.


d) 10 light-years


e) impossible to determine.

c. 10 parsecs

The most distant stars we can measure stellar parallax for are approximately


a) 5 parsecs away.


b) halfway across the Milky Way Galaxy.


c) 100 parsecs away.


d) in the Andromeda Galaxy.


e) 10,000 parsecs away.

c. 100 parsecs away

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


a) All of the above are true.


b) The absolute magnitude of a star is another measure of its luminosity.


c) The magnitude system that we sue now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared.


d) A star with apparent magnitude 1 is brighter than one with apparent magnitude 2.


e) A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth.

a) All of the above are true.


b) The absolute magnitude of a star is another measure of its luminosity.


c) The magnitude system that we sue now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared.


d) A star with apparent magnitude 1 is brighter than one with apparent magnitude 2.


e) A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth.

The spectral sequence sorts stars according to


a) core temperature.


b) luminosity.


c) radius.


d) surface temperature.


e) mass.

d. surface temperature

The spectral sequence in order of decreasing temperature is


a) OFBAGKM.


b) OBAFGKM.


c) OBAGFKM.


d) BAGFKMO.


e) ABFGKMO.

b. OBAFGKM

Why is the spectral sequence of stars not alphabetical?


The letters refer to the initials of the original discovers.


b) The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.


c) Because there is still uncertainty over what generates the energy in stellar cores.


d) They were chosen to fit a mnemonic.


e) Because it refers to stellar masses and these were difficult to measure accurately.

b. The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.

Which of the following statements about spectral types of stars is true?


a) A star with spectral type A is cooler than a star with spectral type B.


b) All of the above are true.


c) A star with spectral type F2 is hotter than a star with spectral type F3.


d) The spectral type of a star can be sued to determine its color.


e) The spectral type of a star can be used to determine its surface temperature.

a) A star with spectral type A is cooler than a star with spectral type B.


b) All of the above are true.


c) A star with spectral type F2 is hotter than a star with spectral type F3.


d) The spectral type of a star can be sued to determine its color.


e) The spectral type of a star can be used to determine its surface temperature.

Suppose you see two main-sequence stars of the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude? (Neglect any effects that might be caused by interstellar dust and gas.)


a) Star 1 is 10 times more distant than Star 2.


b) Without first knowing the distances to these stars, you cannot draw any conclusions about how their true luminosities compare to each other.


c) The luminosity of Star 1 is a factor of 100 less than the luminosity of Star 2.


d) Star 1 is 100 times more distant than Star 2.


e) Star 1 is 100 times nearer than Star 2.

a. Star 1 is 10 times more distant than Star 2.

Which of the following terms is given to a pair of stars that appear to change positions in the sky, indicating that they are orbiting one another?


a) visual binary


b) none of the above


c) spectroscopic binary


d) double star


e) eclipsing binary

a. visual binary

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?


a) none of the above


b) spectroscopic binary


c) visual binary


d) double star


e) eclipsing binary

b. spectroscopic binary

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


a) lower left


b) upper left


c) lower right


d) upper right

c. lower right

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


a) upper left


b) lower right


c) upper right


d) lower left

c. upper right

On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii?


a) lower left


b) upper right


c) upper left


d) lower right

b. upper right

On a Hertzsprung-Russell diagram, where would we find white dwarfs?


a) lower left


b) upper right


c) lower right


d) upper left

a. lower left

On a Hertzsprung-Russell diagram, where would we find red giant stars?


a) upper left


b) lower left


c) upper right


d) lower right

c. upper right

You observe a star in the disk of a Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the


a) apparent brightness of the star in our sky.


b) spectral type of the star.


c) distance to the star.


d) rotation rate of the star.

d. rotation rate of the star

On the main sequence, stars obtain their energy


a) from nuclear fission.


b) by converting helium to carbon, nitrogen, and oxygen.


c) by converting hydrogen to helium.


d) from chemical reactions.


e) from gravitational contraction.

c. by converting hydrogen to helium

A star of spectral type G lives approximately how long on the main sequence?


a) 100 million years


b) 10 billion years


c) 1,000 years


d) 10,000 years


e) 1 million years

b. 10 billion years

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


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 have the same temperature and luminosity as high-mass stars.


d) Low-mass stars are hotter but less luminous than high-mass stars.


e) Low-mass stars are cooler but more luminous than high-mass stars.

a. Low-mass stars are cooler and less luminous than high-mass stars.

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


a) V


b) II


c) III


d) I


e) IV

a. V

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




a) All stars in the cluster have approximately the same mass.


b) There is an approximately equal number of all types of stars in the cluster.


c) All stars in the cluster will evolve similarly.


d) All stars in the cluster are approximately the same color.


e) All stars in the cluster are approximately the same age.

E. All stars in the cluster are approximately the same age.

Cluster ages can be determined from


a) main sequence fitting.


b) visual binaries.


c) spectroscopic binaries.


d) pulsating variable stars.


e) main sequence turnoff.

e) main sequence turnoff

In a pulsating variable star, which characteristic of the star changes dramatically with time?


mass


rotation rate


core temperature


energy-generation process


luminosity

luminosity