Deck 15: Surveying the Stars

Question 1

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)eclipsing binary
C)spectroscopic binary
D)double star
E)none of the above

Answer 1

A

Question 2

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

A)50 parsecs away.
B)500 parsecs away.
C)5,000 parsecs away.
D)halfway across the Milky Way Galaxy.
E)in the Andromeda Galaxy.

Answer 2

B

Question 3

Suppose that you measure the parallax angle for a particular star to be 0.5 arcsecond.The distance to this star is

A)0.5 light-year.
B)0.5 parsec.
C)5 light-years.
D)5 parsecs.
E)2 parsecs.

Answer 3

E

Question 4

Approximately,what basic composition are all stars born with?

A)half hydrogen,half helium,no more than 2 percent heavier elements
B)three-quarters hydrogen,one-quarter helium,no more than 2 percent heavier elements
C)90 percent hydrogen,10 percent helium,no more than 1 percent heavier elements
D)one-quarter hydrogen,three-quarters helium,no more than 2 percent heavier elements
E)98 percent hydrogen,2 percent helium

Question 5

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

A)The spectral type of a star can be used to determine its surface temperature.
B)The spectral type of a star can be used to determine its color.
C)A star with spectral type A is cooler than a star with spectral type B.
D)A star with spectral type F2 is hotter than a star with spectral type F3.
E)All of the above are true.

Question 6

Which of the following persons used the ideas of quantum mechanics to describe why the spectral classification scheme is in order of decreasing temperature?

A)Annie Jump Cannon
B)Williamina Fleming
C)Cecilia Payne-Gaposchkin
D)Henry Draper
E)Edward Pickering

Question 7

The spectral sequence sorts stars according to

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

Question 8

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

A)Annie Jump Cannon
B)Williamina Fleming
C)Cecilia Payne-Gaposchkin
D)Henry Draper
E)Edward Pickering

Question 9

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

A)10 light-years.
B)10 parsecs.
C)0.1 light-year.
D)0.1 parsec.
E)impossible to determine.

Question 10

Which of the following correctly states the luminosity-distance formula?

A)luminosity =
B)apparent brightness =
C)apparent brightness = luminosity × 4π × (distance)²
D)distance =

Question 11

Why is the spectral sequence of stars not alphabetical?

A)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)They were chosen to fit a mnemonic.
D)Because there is still uncertainty over what generates the energy in stellar cores.
E)Because it refers to stellar masses and these were difficult to measure accurately.

Question 12

The spectral sequence in order of decreasing temperature is

A)OFBAGKM.
B)OBAGFKM.
C)OBAFGKM.
D)ABFGKMO.
E)BAGFKMO.

Question 13

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

A)location where they are formed
B)time they are formed
C)luminosity they are formed with
D)mass they are formed with
E)color they are formed with

Question 14

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

A)All stars put out most of their light in the visible range of the spectrum.
B)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.
C)Most stars do not put out light in other ranges of the spectrum.
D)They are identical for most stars.
E)Astronomers are lazy.

Question 15

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)Without first knowing the distances to these stars,you cannot draw any conclusions about how their true luminosities compare to each other.
B)The luminosity of Star 1 is a factor of 100 less than the luminosity of Star 2.
C)Star 1 is 100 times more distant than Star 2.
D)Star 1 is 100 times nearer than Star 2.
E)Star 1 is 10 times more distant than Star 2.

Question 16

A star's luminosity is the

A)apparent brightness of the star in our sky.
B)surface temperature of the star.
C)lifetime of the star.
D)total amount of light that the star will radiate over its entire lifetime.
E)total amount of light that the star radiates each second.

Question 17

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 apparent magnitude 1 is brighter than one with apparent magnitude 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.

Question 18

What are the standard units for apparent brightness?

A)watts
B)joules
C)Newtons
D)watts per second
E)watts per square meter

Question 19

What are the standard units for luminosity?

A)watts
B)joules
C)Newtons
D)kilograms
E)watts per second

Question 20

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.

Question 21

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

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

Question 22

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

A)mass
B)core temperature
C)luminosity
D)energy-generation process
E)rotation rate

Question 23

Why are Cepheid variables so important for measuring distances in astronomy?

A)They all have the same luminosity.
B)They all have the same period.
C)Their luminosity can be inferred from their period.
D)They are close enough to have a detectable parallax.
E)They are circumpolar like Polaris,the North Star.

Question 24

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

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

Question 25

On the main sequence,stars obtain their energy

A)from chemical reactions.
B)from gravitational contraction.
C)by converting hydrogen to helium.
D)by converting helium to carbon,nitrogen,and oxygen.
E)from nuclear fission.

Question 26

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

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

Question 27

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 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.

Question 28

Which of the following characteristics of stars has the greatest range in values?

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

Question 29

On a Hertzsprung-Russell diagram,where on the main sequence would we find stars that have the greatest mass?

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

Question 30

You observe a star in the disk of the 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)spectral type of the star.
B)distance to the star.
C)apparent brightness of the star in our sky.
D)rotation rate of the star.

Question 31

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

A)1,000 years
B)10,000 years
C)1 million years
D)100 million years
E)10 billion years

Question 32

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

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

Question 33

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)visual binary
B)eclipsing binary
C)spectroscopic binary
D)double star
E)none of the above

Question 34

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

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

Question 35

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

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

Question 36

The faintest star visible to the naked eye has an apparent visual magnitude of about

A)10.
B)6.
C)1.
D)0.
E)-6.

Question 37

Which of the following is the most common type of main-sequence star?

A)an O star
B)an A star
C)an F star
D)an M star
E)a G star

Question 38

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

A)All stars in the cluster are approximately the same color.
B)All stars in the cluster are approximately the same age.
C)All stars in the cluster have approximately the same mass.
D)All stars in the cluster will evolve similarly.
E)There is an approximately equal number of all types of stars in the cluster.

Question 39

Which of the following best describes the axes of a Hertzsprung-Russell (H-R)diagram?

A)surface temperature on the horizontal axis and luminosity on the vertical axis
B)mass on the horizontal axis and luminosity on the vertical axis
C)surface temperature on the horizontal axis and radius on the vertical axis
D)mass on the horizontal axis and stellar age on the vertical axis
E)interior temperature on the horizontal axis and mass on the vertical axis

Question 40

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

A)1,000 years
B)10,000 years
C)10 million years
D)100 million years
E)1 billion years

Question 41

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 half Earth's distance from the Sun.

Question 42

Most stars on the main sequence fuse hydrogen into helium in their cores,but some do not.

Question 43

The more distant a star,the smaller its parallax.

Question 44

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

Question 45

Two stars have the same spectral type.Star X is in luminosity class III,while Star Y is in luminosity class V.Therefore,Star X is larger in radius than Star Y.

Question 46

A 10-solar-mass star is about ten times more luminous than a 1-solar-mass star.

Question 47

Which of the following statements about a globular cluster is true?

A)All stars in the cluster are approximately at the same stage in evolution.
B)Most of the stars in the cluster are younger than 10 billion years old.
C)Most stars in the cluster are yellow or reddish in color.
D)All stars in the cluster have approximately the same mass.
E)There is an approximately equal number of all types of stars in the cluster.

Question 48

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

Question 49

Massive,more luminous stars have shorter lives than their smaller,dimmer counterparts.

Question 50

Some stars are cool enough to have molecules in their atmosphere.

Question 51

We can measure stellar parallax for most stars in our galaxy.

Question 52

We can measure the radii of stars in an eclipsing binary system,in addition to the masses.

Question 53

Two stars have the same luminosity.Star X is spectral type F,while Star Y is spectral type K.Therefore,Star X is larger in radius than Star Y.

Question 54

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

Question 55

All stars spend approximately the same amount of time on the main sequence.

Question 56

Where do we find our star on the H-R diagram?

A)In the middle of the main sequence
B)On the far left of the main sequence
C)With the red giants
D)On the lower left

Question 57

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

Question 58

If the distance between us and a star is doubled,the apparent brightness is decreased by a factor of four.

Question 59

Cluster ages can be determined from

A)main sequence fitting.
B)main sequence turnoff.
C)pulsating variable stars.
D)spectroscopic binaries.
E)visual binaries.

Question 60

In order to understand star clusters,we need to be able to estimate their ages.What technique do scientists use for this?

A)radioisotope dating
B)counting the planets that have formed around the largest stars
C)finding the main-sequence turnoff point of the stars
D)calculating orbital parameters using Kepler's Laws
E)measuring its parallax

Question 61

Two stars,Fred and Barney,are of the same size.Fred has spectral type F,while Barney has spectral type B.Which one is more luminous?

Question 62

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 cool and dim?

Question 63

Which is brighter in our sky,a star with apparent magnitude 2 or a star with apparent magnitude 7? By how much is the star brighter?

Question 64

Refer to the choices in the table for the following questions.

Which star appears brightest in the sky?

Question 65

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?

Question 66

Refer to the choices in the table for the following questions.

Which star has the largest radius?

Question 67

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 Earth's distance from the Sun.

Question 68

Refer to the choices in the table for the following questions.

Which star is the most distant?

Question 69

Refer to the choices in the table for the following questions.

Which star is most similar to the Sun?

Question 70

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 Earth's distance from the Sun.

Question 71

Refer to the choices in the table for the following questions.

Which star looks reddest in color?

Question 72

Refer to the choices in the table for the following questions.

Which star looks bluest in color?

Question 73

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 the most common type of stars?

Question 74

Refer to the choices in the table for the following questions.

Which star is emitting the most ultraviolet light per unit area?

Question 75

Two stars,Tom and Jerry,have the same spectral type.Tom is luminosity class V and Jerry is luminosity class I.Which star is bigger? Which star is more luminous? Which star has a hotter surface temperature? Explain your answers.

Question 76

Refer to the choices in the table for the following questions.

Which star has the greatest luminosity?

Question 77

Refer to the choices in the table for the following questions.

Which star has the lowest surface temperature?

Question 78

Which has a greater luminosity,a star with absolute magnitude +4 or a star with absolute magnitude -6? By how much is it brighter?

Question 79

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 but dim?

Question 80

Refer to the choices in the table for the following questions.

Which star has the highest surface temperature?