Question 1

Suppose that Hubble's constant were 20 kilometers per second per million light-years.How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is due only to Hubble's law. )

Accepted Answer

A)  away from us at 200 km/s
B)  toward us at 2,000 km/s
C)  away from us at 2,000 km/s
D)  away from us at 20,000 km/sE) A) and D)
F) None of the above

Question 2

Dr.X believes that the Hubble constant is H₀ = 55 km/s/Mpc.Dr.Y believes it is H₀ = 80 km/s/Mpc.Which statement below automatically follows?

Accepted Answer

A)  Dr.X believes that the universe is expanding,but Dr.Y does not.
B)  Dr.X believes that the Andromeda Galaxy (a member of our Local Group) is moving away from us at a slower speed than Dr.Y believes.
C)  Dr.X believes that the universe is older than Dr.Y believes.
D)  Dr.X believes that the universe will someday stop expanding,while Dr.Y believes it will expand forever.
E)  Dr.X believes that the universe has a much higher density than Dr.Y believes.F) A) and C)
G) A) and E)

Question 3

The larger the value of Hubble's constant,the more rapid the expansion of the universe and hence the younger the universe.

Accepted Answer

A) True 
 B)False

Question 4

If we say that a galaxy has a lookback time of 1 billion years,we mean that

Accepted Answer

A)  its light traveled through space for 1 billion years to reach us.
B)  is now 1 billion light-years away.
C)  it was 1 billion light-years away when the light left the galaxy.
D)  it is 400 million years old.E) C) and D)
F) A) and B)

Question 5

List at least three qualities that would tend to make a type of astronomical object useful as a standard candle.

Accepted Answer

Answers will vary,but some of the key pr...

Question 6

What is a Cepheid variable?

Accepted Answer

A)  It is a bright source of variable X-ray emission,thought to harbor a supermassive black hole.
B)  It is a type of very luminous star that makes an excellent standard candle.
C)  It is a main-sequence star of spectral type B5.
D)  It is a type of galaxy that varies in its light output.E) B) and D)
F) B) and C)

Question 7

How does the age of the universe depend on Hubble's constant,and why?

Accepted Answer

The larger the value of Hubble's constan...

Question 8

Based on the number of galaxies visible in the Hubble Deep Field (Figure 20.1 in your textbook) ,the estimated number of galaxies in our observable universe is

Accepted Answer

A)  about 50,000.
B)  about 100 million.
C)  about 100 billion.
D)  an infinite number.E) A) and B)
F) None of the above

Question 9

Recall that Hubble's law is written v = H₀d,where v is the recession velocity of a galaxy located a distance d away from us,and H₀ is Hubble's constant.Suppose H₀ = 55 km/s/Mpc.How fast would a galaxy located 500 megaparsecs distant be receding from us? Show all work clearly,and state your final answer with a complete sentence.Give the speed in units of kilometers per second and as a percentage of the speed of light.

Accepted Answer

v = H₀d = (55

(500 Mpc)
=27.5...

Question 10

Given that the universe is about 14 billion years old,which of the following statements is logically valid?

Accepted Answer

A)  All galaxies nearby us are about 14 billion years old.
B)  All galaxies that we can see are about 14 billion years old.
C)  All galaxies that we see have an age that is approximately equal to the age of the universe today,minus the lookback time (or light travel time) corresponding to the redshift of that galaxy.
D)  The oldest galaxies we see at great distances are younger than the oldest galaxies we see nearby.E) None of the above
F) A) and D)

Question 11

Hubble's constant is about 22 km/s/million light-years,implying an age of about 14 billion years for the universe.If Hubble's constant were 11 km/s/million light-years,the age of the universe would be about

Accepted Answer

A)  7 billion years.
B)  14 billion years.
C)  28 billion years.
D)  Impossible to say,because Hubble's constant has no relationship to the age of the universe.E) A) and C)
F) None of the above

Question 12

Spectral lines from Galaxy B are redshifted from their rest wavelengths twice as much as the spectral lines from Galaxy A.According to Hubble's law,what can you say about their approximate relative distances?

Accepted Answer

A)  Galaxy A is twice as far as Galaxy B.
B)  Galaxy B is four times as far as Galaxy A.
C)  Galaxy A is four times as far as Galaxy B.
D)  Galaxy B is twice as far as Galaxy A.
E)  Not enough information to say-you need to know Hubble's constant to answer this question.F) D) and E)
G) C) and E)

Question 13

Hubble's "constant" is constant in

Accepted Answer

A)  time.
B)  space.
C)  space and time.
D)  our Galaxy but different in others.E) B) and C)
F) A) and B)

Question 14

The disk component of a spiral galaxy includes which of the following parts?

Accepted Answer

A)  halo
B)  bulge
C)  spiral arms
D)  globular clusters
E)  all of the aboveF) A) and D)
G) A) and C)

Question 15

Overall,what is our most accurate technique for measuring the distance to a nearby star?

Accepted Answer

A)  radar ranging
B)  stellar parallax
C)  Hubble's law
D)  white dwarf supernovaeE) None of the above
F) B) and C)

Question 16

Based on current estimates of the value of Hubble's constant,how old is the universe?

Accepted Answer

A)  between 4 and 6 billion years old
B)  between 8 and 12 billion years old
C)  between 12 and 16 billion years old
D)  between 16 and 20 billion years old
E)  between 20 and 40 billion years oldF) B) and C)
G) A) and C)

Question 17

Why can't we see past the cosmological horizon?

Accepted Answer

A)  Beyond the cosmological horizon,we would be looking back to a time before the universe was born.
B)  We do not have big enough telescopes.
C)  The cosmological horizon is infinitely far away,and we can't see to infinity.
D)  Every galaxy in the entire universe (not just the observable universe) exists within the cosmological horizon,so there's nothing to see beyond it.E) B) and C)
F) A) and D)

Question 18

If we were to measure Hubble's constant 10 billion years in the future,we would find it exactly the same as it is today.

Accepted Answer

A) True 
 B)False

Question 19

Galaxies with disks but no evident spiral arms are called

Accepted Answer

A)  irregular galaxies.
B)  lenticular galaxies.
C)  barred spiral galaxies.
D)  spheroidal components.E) A) and D)
F) A) and C)

Question 20

Which of the following statements about galaxies is true?

Accepted Answer

A)  Small galaxies outnumber large galaxies and produce most of the light in the universe.
B)  Small galaxies outnumber large galaxies but large galaxies produce most of the light in the universe.
C)  There is an approximately equal number of small and large galaxies in the universe and together they each contribute an equal amount of light.
D)  Most galaxies in the universe are about the same size as the Milky Way.
E)  Galaxies come in a wide variety of shapes and sizes but are all very blue in color.F) A) and D)
G) A) and E)

Exam 20: Galaxies and the Foundations of Modern Cosmology

Hubble's "constant" is constant in

Correct Answer
verified

Which of the following statements about galaxies is true?

Correct Answer
verified

What is a Cepheid variable?

Correct Answer
verified

If we were to measure Hubble's constant 10 billion years in the future,we would find it exactly the same as it is today.

Correct Answer
verified

Hubble's constant is about 22 km/s/million light-years,implying an age of about 14 billion years for the universe.If Hubble's constant were 11 km/s/million light-years,the age of the universe would be about

Correct Answer
verified

Suppose that Hubble's constant were 20 kilometers per second per million light-years.How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is due only to Hubble's law. )

Correct Answer
verified

The larger the value of Hubble's constant,the more rapid the expansion of the universe and hence the younger the universe.

Correct Answer
verified

The disk component of a spiral galaxy includes which of the following parts?

Correct Answer
verified

Galaxies with disks but no evident spiral arms are called

Correct Answer
verified

Dr.X believes that the Hubble constant is H₀ = 55 km/s/Mpc.Dr.Y believes it is H₀ = 80 km/s/Mpc.Which statement below automatically follows?

Correct Answer
verified

If we say that a galaxy has a lookback time of 1 billion years,we mean that

Correct Answer
verified

List at least three qualities that would tend to make a type of astronomical object useful as a standard candle.

Correct Answer
verified
Answers will vary,but some of the key pr...
View Answer

How does the age of the universe depend on Hubble's constant,and why?

Correct Answer
verified
The larger the value of Hubble's constan...
View Answer

Why can't we see past the cosmological horizon?

Correct Answer
verified

Based on current estimates of the value of Hubble's constant,how old is the universe?

Correct Answer
verified

Correct Answer
verified
v = H₀d = (55 (500 Mpc)
=27.5...
View Answer

Overall,what is our most accurate technique for measuring the distance to a nearby star?

Correct Answer
verified

Based on the number of galaxies visible in the Hubble Deep Field (Figure 20.1 in your textbook) ,the estimated number of galaxies in our observable universe is

Correct Answer
verified

Given that the universe is about 14 billion years old,which of the following statements is logically valid?

Correct Answer
verified

Spectral lines from Galaxy B are redshifted from their rest wavelengths twice as much as the spectral lines from Galaxy A.According to Hubble's law,what can you say about their approximate relative distances?

Correct Answer
verified

Exam 20: Galaxies and the Foundations of Modern Cosmology

Hubble's "constant" is constant in

Correct AnswerverifiedShow Answer

Which of the following statements about galaxies is true?

Correct AnswerverifiedShow Answer

What is a Cepheid variable?

Correct AnswerverifiedShow Answer

If we were to measure Hubble's constant 10 billion years in the future,we would find it exactly the same as it is today.

Correct AnswerverifiedShow Answer

Hubble's constant is about 22 km/s/million light-years,implying an age of about 14 billion years for the universe.If Hubble's constant were 11 km/s/million light-years,the age of the universe would be about

Correct AnswerverifiedShow Answer

Suppose that Hubble's constant were 20 kilometers per second per million light-years.How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is due only to Hubble's law. )

Correct AnswerverifiedShow Answer

The larger the value of Hubble's constant,the more rapid the expansion of the universe and hence the younger the universe.

Correct AnswerverifiedShow Answer

The disk component of a spiral galaxy includes which of the following parts?

Correct AnswerverifiedShow Answer

Galaxies with disks but no evident spiral arms are called

Correct AnswerverifiedShow Answer

Dr.X believes that the Hubble constant is H₀ = 55 km/s/Mpc.Dr.Y believes it is H₀ = 80 km/s/Mpc.Which statement below automatically follows?

Correct AnswerverifiedShow Answer

If we say that a galaxy has a lookback time of 1 billion years,we mean that

Correct AnswerverifiedShow Answer

List at least three qualities that would tend to make a type of astronomical object useful as a standard candle.

Correct AnswerverifiedAnswers will vary,but some of the key pr...View AnswerShow Answer

How does the age of the universe depend on Hubble's constant,and why?

Correct AnswerverifiedThe larger the value of Hubble's constan...View AnswerShow Answer

Why can't we see past the cosmological horizon?

Correct AnswerverifiedShow Answer

Based on current estimates of the value of Hubble's constant,how old is the universe?

Correct AnswerverifiedShow Answer

Correct Answerverifiedv = H₀d = (55 (500 Mpc)=27.5...View AnswerShow Answer

Overall,what is our most accurate technique for measuring the distance to a nearby star?

Correct AnswerverifiedShow Answer

Based on the number of galaxies visible in the Hubble Deep Field (Figure 20.1 in your textbook) ,the estimated number of galaxies in our observable universe is

Correct AnswerverifiedShow Answer

Given that the universe is about 14 billion years old,which of the following statements is logically valid?

Correct AnswerverifiedShow Answer

Spectral lines from Galaxy B are redshifted from their rest wavelengths twice as much as the spectral lines from Galaxy A.According to Hubble's law,what can you say about their approximate relative distances?

Correct AnswerverifiedShow Answer

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verified
Answers will vary,but some of the key pr...
View Answer

Correct Answer
verified
The larger the value of Hubble's constan...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
v = H₀d = (55 (500 Mpc)
=27.5...
View Answer

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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