Question 1

In size, the Milky Way Galaxy is:

Accepted Answer

A)  one of the largest galaxies, with no other galaxy known to be much larger.
B)  one of the smallest galaxies, with few others known to be much smaller.
C)  a typical galaxy, with many others known to be larger and many known to be smaller.
D)  virtually the entire universe, with very few objects known to be outside it.E) All of the above
F) B) and C)

Question 2

What does the Hubble law tell us, if H0 is a constant?

Accepted Answer

A)  H0 × recessional speed = distance
B)  recessional speed = H0 = constant
C)  distance × recessional speed = H0
D)  recessional speed = H0 × distanceE) C) and D)
F) All of the above

Question 3

How does the intrinsic brightness or luminosity of a Cepheid variable star compare to that of our Sun?

Accepted Answer

A)  much less, about 1/10, because it is a variable star
B)  larger, by 100
C)  about the same
D)  much larger, by 104E) C) and D)
F) B) and D)

Question 4

All of the following systems are gravitationally bound EXCEPT:

Accepted Answer

A)  open clusters.
B)  globular clusters.
C)  clusters of galaxies.
D)  superclusters of galaxies.E) B) and C)
F) All of the above

Question 5

Maser light in distant galaxies can be used to calculate the distance to the source. In what spectral range do we observe this light?

Accepted Answer

A)  ultraviolet
B)  visible
C)  infrared
D)  microwaveE) All of the above
F) A) and D)

Question 6

The discovery of the expanding universe began in 1914 when V. M. Slipher realized that 11 of the 15 spiral "nebulae" he imaged showed redshifts. Why only 11?

Accepted Answer

A)  His measuring instruments were not fine enough to show the redshifts in the others.
B)  He included nearby open clusters in his sample.
C)  By chance he included in his sample active galaxies with jets. The redshifts of the galaxies were masked by the blueshifts of the jets.
D)  He was looking at nearby galaxies in the Local Group, and many of these have intrinsic velocities that are larger than their participation in the Hubble flow.E) A) and B)
F) A) and C)

Question 7

A Cepheid variable is observed in a distant galaxy. Its period is 30 days, and its apparent magnitude of 19.8 corresponds to a brightness ratio of b/bŸ = 2.35 x 10-19. How far away is it?

Accepted Answer

A)  1 kpc
B)  180 kpc
C)  1 Mpc
D)  13.6 MpcE) A) and C)
F) All of the above

Question 8

A Cepheid variable is observed in a galaxy 1 Mpc distant. It has a period of 30 days. What is its apparent magnitude?

Accepted Answer

A)  12.8
B)  15.9
C)  19.8
D)  21.7E) C) and D)
F) A) and D)

Question 9

Based on the most accurate measurements to date, what is believed to be the value of the Hubble constant?

Accepted Answer

A)  between 50 and 60 (km/s) /Mpc
B)  between 100 and 120 (km/s) /Mpc
C)  between 70 and 75 (km/s) /Mpc
D)  between 80 and 90 (km/s) /MpcE) All of the above
F) A) and B)

Question 10

Which one of the following entities is NOT formed by the collapse of a large mass of gas and dust?

Accepted Answer

A)  a star
B)  an open cluster
C)  a globular cluster
D)  a galaxyE) A) and D)
F) None of the above

Question 11

One unusual result of galaxy interactions is:

Accepted Answer

A)  large numbers of gamma-ray bursters.
B)  at least a dozen spiral arms.
C)  radio wavelength emissions from cold gas.
D)  globular clusters dominated by blue supergiants.E) A) and C)
F) All of the above

Question 12

The Whirlpool Galaxy (M51)  (see Figure 23-1 of Universe, 11th ed.(in the text) )  shows H II regions outlining the spiral arms. What causes their red color?

Accepted Answer

A)  H II regions have the characteristic red Hα line excited by radiation from the large, hot, newly formed stars in the spiral arms.
B)  These H II regions are dominated by red giants and supergiants.
C)  The spiral arms are rotating rapidly away from us, and their radiation is Doppler shifted into the red.
D)  Gas and dust in the plane of the galaxy cause interstellar reddening (extinction)  as the light passes through the galaxy on its way toward us.E) A) and B)
F) A) and C)

Question 13

How much of the mass of a galaxy plays a role in emitting radiation into space?

Accepted Answer

A)  10%
B)  50%
C)  only about 1%
D)  almost 100%E) A) and C)
F) B) and C)

Question 14

What is the Great Attractor?

Accepted Answer

A)  an empty point at the center of one of the largest voids, now believed to be the center of the universe
B)  the largest known black hole, believed to be the site of the original Big Bang
C)  a particularly massive cluster of galaxies
D)  the name given to the combined gravitational effects of the nearest several dozen clusters of galaxiesE) All of the above
F) A) and B)

Question 15

The Hubble classification for a galaxy having loosely wound spiral arms originating at the ends of a bar through the central bulge is:

Accepted Answer

A)  Sb.
B)  SBa.
C)  S0.
D)  SBc.E) A) and C)
F) A) and B)

Question 16

Astronomers often speak of redshift z rather than distance d. If the speeds are a small fraction of the speed of light, the relationship between d and z is:

Accepted Answer

A)  d = H0 z.
B)  d = H0/(cz) .
C)  d = z/(H0 c) 
D)  d = zc/H0.E) B) and C)
F) A) and D)

Question 17

How many large spiral galaxies are there in the Local Group of galaxies?

Accepted Answer

A)  The Milky Way Galaxy is the only one.
B)  There are only two, Andromeda and the Milky Way.
C)  There are three.
D)  We really don't know how many because some could be hidden unseen on the other side of our galaxy, cut off from our view by clouds of gas and dust.E) A) and B)
F) A) and C)

Question 18

Which of the following did Edwin Hubble NOT contribute to our understanding of galaxies and their behavior?

Accepted Answer

A)  observations of Cepheid variable stars in spiral "nebulae" and their interpretation
B)  a relationship between distance to galaxies and their apparent velocity of recession
C)  determination of the ages of galaxies and the correct sequence of evolutionary progress of galaxies
D)  a classification scheme for galaxy typesE) A) and D)
F) B) and D)

Question 19

The Hubble relationship shows a proportionality between the distance to a galaxy and the:

Accepted Answer

A)  width of the 21-cm radio emission line from hydrogen.
B)  parallax angle change of the galaxy as Earth moves through 1 year.
C)  angular diameter of the galaxy as seen from Earth.
D)  overall redshift of a galaxy's spectrum.E) All of the above
F) A) and B)

Question 20

What method is used to determine the distances of very remote galaxies?

Accepted Answer

A)  use of their spectral redshifts and the Hubble law
B)  measurement of the angular size of the galaxy and an assumption about the actual physical size of the galaxy
C)  measurement of the apparent brightness and period of Cepheid variable stars within the galaxies
D)  comparison of their apparent and absolute magnitudesE) B) and C)
F) C) and D)

Exam 23: Galaxies

What method is used to determine the distances of very remote galaxies?

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What does the Hubble law tell us, if H0 is a constant?

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A Cepheid variable is observed in a distant galaxy. Its period is 30 days, and its apparent magnitude of 19.8 corresponds to a brightness ratio of b/bŸ = 2.35 x 10-19. How far away is it?

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In size, the Milky Way Galaxy is:

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All of the following systems are gravitationally bound EXCEPT:

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The Hubble relationship shows a proportionality between the distance to a galaxy and the:

Correct AnswerverifiedShow Answer

Maser light in distant galaxies can be used to calculate the distance to the source. In what spectral range do we observe this light?

Correct AnswerverifiedShow Answer

How much of the mass of a galaxy plays a role in emitting radiation into space?

Correct AnswerverifiedShow Answer

Astronomers often speak of redshift z rather than distance d. If the speeds are a small fraction of the speed of light, the relationship between d and z is:

Correct AnswerverifiedShow Answer

Based on the most accurate measurements to date, what is believed to be the value of the Hubble constant?

Correct AnswerverifiedShow Answer

The discovery of the expanding universe began in 1914 when V. M. Slipher realized that 11 of the 15 spiral "nebulae" he imaged showed redshifts. Why only 11?

Correct AnswerverifiedShow Answer

Which of the following did Edwin Hubble NOT contribute to our understanding of galaxies and their behavior?

Correct AnswerverifiedShow Answer

How does the intrinsic brightness or luminosity of a Cepheid variable star compare to that of our Sun?

Correct AnswerverifiedShow Answer

A Cepheid variable is observed in a galaxy 1 Mpc distant. It has a period of 30 days. What is its apparent magnitude?

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How many large spiral galaxies are there in the Local Group of galaxies?

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What is the Great Attractor?

Correct AnswerverifiedShow Answer

One unusual result of galaxy interactions is:

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Which one of the following entities is NOT formed by the collapse of a large mass of gas and dust?

Correct AnswerverifiedShow Answer

The Hubble classification for a galaxy having loosely wound spiral arms originating at the ends of a bar through the central bulge is:

Correct AnswerverifiedShow Answer

The Whirlpool Galaxy (M51) (see Figure 23-1 of Universe, 11th ed.(in the text) ) shows H II regions outlining the spiral arms. What causes their red color?

Correct AnswerverifiedShow Answer

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What does the Hubble law tell us, if H₀ is a constant?

Correct Answer
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A Cepheid variable is observed in a distant galaxy. Its period is 30 days, and its apparent magnitude of 19.8 corresponds to a brightness ratio of b/b_Ÿ = 2.35 x 10^-19. How far away is it?

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