Question 1

Which of the following statements about types of galaxies is not true?

Accepted Answer

A) Spiral galaxies have younger stars than elliptical galaxies. 
B) Among the large galaxies in the universe outside of clusters,most are spiral. 
C) Large elliptical galaxies are more common in clusters of galaxies than they are outside of clusters. 
D) Elliptical galaxies are bluer and contain more dust than spiral galaxies. 
A) Spiral galaxies have younger stars than elliptical galaxies. 
B) Among the large galaxies in the universe outside of clusters,most are spiral. 
C) Large elliptical galaxies are more common in clusters of galaxies than they are outside of clusters. 
D) Elliptical galaxies are bluer and contain more dust than spiral galaxies.

Question 2

Explain how we estimate that there are about 50-100 billion galaxies in the observable universe.

Accepted Answer

Obviously it's impossible to count so ma

Question 3

Explain why we observe distant galaxies to be moving away from us and therefore believe that the universe is expanding,but we don't see individual galaxies or clusters expanding.

Accepted Answer

The pull of gravity works to slow the ex

Question 4

Suppose we observe a Cepheid variable in a distant galaxy.The Cepheid brightens and dims with a regular period of about 10 days.What can we learn from this observation?

Accepted Answer

A) It will allow us to calculate the rotation rate of the galaxy. 
B) It will allow us to determine the mass of the galaxy. 
C) We can learn the distance to the galaxy. 
D) Under the rules of the International Astronomical Union,we will be entitled to naming rights for the galaxy. 
A) It will allow us to calculate the rotation rate of the galaxy. 
B) It will allow us to determine the mass of the galaxy. 
C) We can learn the distance to the galaxy. 
D) Under the rules of the International Astronomical Union,we will be entitled to naming rights for the galaxy.

Question 5

A standard candle is

Accepted Answer

A) a 7-cm-long wax candle. 
B) another name for a main-sequence star. 
C) another name for a barred-spiral galaxy. 
D) a light source of known luminosity. 
A) a 7-cm-long wax candle. 
B) another name for a main-sequence star. 
C) another name for a barred-spiral galaxy. 
D) a light source of known luminosity.

Question 6

What is the most accurate way to determine the distance to a nearby star?

Accepted Answer

A) radar ranging 
B) stellar parallax 
C) using Cepheid variables 
D) Hubble's law 
A) radar ranging 
B) stellar parallax 
C) using Cepheid variables 
D) Hubble's law

Question 7

Suppose that we suddenly discovered that all these years we'd been wrong about the distance from Earth to the Sun,and it is actually 10% greater than we'd thought.How would that affect our estimate of the distance to the Andromeda Galaxy?

Accepted Answer

A) It would not have any effect on our estimate of the distance to the Andromeda Galaxy. 
B) It would mean the distance to the Andromeda Galaxy is also 10% greater than we thought. 
C) It would mean the distance to the Andromeda Galaxy is 10% less than we thought. 
D) It would mean that all the objects we've assumed are standard candles really are not good standard candles,and therefore that we have no idea of the true distance to the Andromeda Galaxy. 
A) It would not have any effect on our estimate of the distance to the Andromeda Galaxy. 
B) It would mean the distance to the Andromeda Galaxy is also 10% greater than we thought. 
C) It would mean the distance to the Andromeda Galaxy is 10% less than we thought. 
D) It would mean that all the objects we've assumed are standard candles really are not good standard candles,and therefore that we have no idea of the true distance to the Andromeda Galaxy.

Question 8

Most large galaxies in the universe are

Accepted Answer

A) elliptical. 
B) spiral or lenticular. 
C) irregular. 
D) abnormal. 
A) elliptical. 
B) spiral or lenticular. 
C) irregular. 
D) abnormal.

Question 9

Dr.Smith believes that the Hubble constant is H₀ = 70 km/s/Mpc.Dr.Jones believes it is H₀ = 50 km/s/Mpc.Which statement below automatically follows?

Accepted Answer

A) Dr.Smith believes that the universe is expanding,but Dr.Jones does not. 
B) Dr.Smith believes that the Andromeda Galaxy (a member of our Local Group)is moving away from us at a faster speed than Dr.Jones believes. 
C) Dr.Smith believes that the universe is older than Dr.Jones believes. 
D) Dr.Smith believes that the universe is younger than Dr.Jones believes. 
E) Dr.Smith believes that the universe will someday stop expanding,while Dr.Jones believes it will expand forever. 
A) Dr.Smith believes that the universe is expanding,but Dr.Jones does not. 
B) Dr.Smith believes that the Andromeda Galaxy (a member of our Local Group)is moving away from us at a faster speed than Dr.Jones believes. 
C) Dr.Smith believes that the universe is older than Dr.Jones believes. 
D) Dr.Smith believes that the universe is younger than Dr.Jones believes. 
E) Dr.Smith believes that the universe will someday stop expanding,while Dr.Jones believes it will expand forever.

Question 10

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 = 65 km/s/Mpc.How fast would a galaxy located 500 megaparsecs distant be receding from us?

Accepted Answer

A) 65 km/s 
B) 65 Mpc/s 
C) 32,500 km/s 
D) 9 km/s 
E) 0.65 times the speed of light 
A) 65 km/s 
B) 65 Mpc/s 
C) 32,500 km/s 
D) 9 km/s 
E) 0.65 times the speed of light

Question 11

Which of the following types of galaxies are most commonly found in large clusters?

Accepted Answer

A) spirals 
B) ellipticals 
C) lenticulars 
D) irregulars 
A) spirals 
B) ellipticals 
C) lenticulars 
D) irregulars

Question 12

What makes white-dwarf supernovae good standard candles?

Accepted Answer

A) They are very bright,so they can be used to determine the distances to galaxies billions of light-years away. 
B) They should all have approximately the same luminosity. 
C) They occur so frequently that we can use them to measure the distances to virtually all galaxies. 
D) We have had several occur close to us in the Milky Way,so we have been able to determine their luminosities very accurately. 
E) both A and B 
A) They are very bright,so they can be used to determine the distances to galaxies billions of light-years away. 
B) They should all have approximately the same luminosity. 
C) They occur so frequently that we can use them to measure the distances to virtually all galaxies. 
D) We have had several occur close to us in the Milky Way,so we have been able to determine their luminosities very accurately. 
E) both A and B

Question 13

Although the entire universe may be much larger than our observable universe,we can see only within our observable universe.The "boundary" of our observable universe is called

Accepted Answer

A) the cosmological horizon. 
B) the Big Bang. 
C) the lookback time. 
D) the singularity. 
A) the cosmological horizon. 
B) the Big Bang. 
C) the lookback time. 
D) the singularity.

Question 14

What is the best way to determine a galaxy's redshift?

Accepted Answer

A) Find the galaxy's apparent distance,and look up the redshift based on Hubble's law. 
B) Find the color of the galaxy,and estimate its distance based on how red the galaxy is. 
C) Take a spectrum of the galaxy,and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory. 
D) Measure the magnitude of the galaxy,estimate its distance,and calculate its redshift using Hubble's law. 
A) Find the galaxy's apparent distance,and look up the redshift based on Hubble's law. 
B) Find the color of the galaxy,and estimate its distance based on how red the galaxy is. 
C) Take a spectrum of the galaxy,and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory. 
D) Measure the magnitude of the galaxy,estimate its distance,and calculate its redshift using Hubble's law.

Question 15

Although it is difficult to tell from our vantage point inside the galaxy,astronomers suspect that the Milky Way is a barred spiral.

Accepted Answer

A) True 
 B)False

Question 16

Why are Cepheid variables important?

Accepted Answer

A) Cepheid variables are stars that vary in brightness because they harbor a black hole. 
B) Cepheids are pulsating variable stars,and their pulsation periods are directly related to their true luminosities.Hence,we can use Cepheids as "standard candles" for distance measurements. 
C) Cepheids are a type of young galaxy that helps us understand how galaxies form. 
D) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future. 
A) Cepheid variables are stars that vary in brightness because they harbor a black hole. 
B) Cepheids are pulsating variable stars,and their pulsation periods are directly related to their true luminosities.Hence,we can use Cepheids as "standard candles" for distance measurements. 
C) Cepheids are a type of young galaxy that helps us understand how galaxies form. 
D) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future.

Question 17

Why are galaxies in the blue cloud blue?

Accepted Answer

A) They contain hot,young stars that signify active star formation. 
B) They are moving slower than stars in the red cloud. 
C) They contain lots of dust that cause the bluish color. 
D) They contain cold,dying stars that are fading to black. 
A) They contain hot,young stars that signify active star formation. 
B) They are moving slower than stars in the red cloud. 
C) They contain lots of dust that cause the bluish color. 
D) They contain cold,dying stars that are fading to black.

Question 18

Which statement below correctly describes the relationship between expansion rate and age for the universe?

Accepted Answer

A) The faster the rate of expansion,the younger the age of the universe. 
B) The faster the rate of expansion,the older the age of the universe. 
C) Age is independent of the expansion rate. 
A) The faster the rate of expansion,the younger the age of the universe. 
B) The faster the rate of expansion,the older the age of the universe. 
C) Age is independent of the expansion rate.

Question 19

Which of the following is not one of the three major categories of galaxies?

Accepted Answer

A) elliptical galaxies 
B) globular galaxies 
C) spiral galaxies 
D) irregular galaxies 
A) elliptical galaxies 
B) globular galaxies 
C) spiral galaxies 
D) irregular galaxies

Question 20

The most basic difference between elliptical galaxies and spiral galaxies is that

Accepted Answer

A) elliptical galaxies lack anything resembling the halo of a spiral galaxy. 
B) elliptical galaxies have a spheroidal component (of stars distributed spherically about the galactic center),and spiral galaxies do not. 
C) elliptical galaxies lack anything resembling the disk of a spiral galaxy. 
D) elliptical galaxies are very old and spiral galaxies are very young. 
A) elliptical galaxies lack anything resembling the halo of a spiral galaxy. 
B) elliptical galaxies have a spheroidal component (of stars distributed spherically about the galactic center),and spiral galaxies do not. 
C) elliptical galaxies lack anything resembling the disk of a spiral galaxy. 
D) elliptical galaxies are very old and spiral galaxies are very young.

Exam 20: Galaxies and the Foundations of Modern Cosmology

Which of the following statements about types of galaxies is not true?

Explain how we estimate that there are about 50-100 billion galaxies in the observable universe.

Explain why we observe distant galaxies to be moving away from us and therefore believe that the universe is expanding,but we don't see individual galaxies or clusters expanding.

Suppose we observe a Cepheid variable in a distant galaxy.The Cepheid brightens and dims with a regular period of about 10 days.What can we learn from this observation?

A standard candle is

What is the most accurate way to determine the distance to a nearby star?

Suppose that we suddenly discovered that all these years we'd been wrong about the distance from Earth to the Sun,and it is actually 10% greater than we'd thought.How would that affect our estimate of the distance to the Andromeda Galaxy?

Most large galaxies in the universe are

Dr.Smith believes that the Hubble constant is H₀ = 70 km/s/Mpc.Dr.Jones believes it is H₀ = 50 km/s/Mpc.Which statement below automatically follows?

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 = 65 km/s/Mpc.How fast would a galaxy located 500 megaparsecs distant be receding from us?

Which of the following types of galaxies are most commonly found in large clusters?

What makes white-dwarf supernovae good standard candles?

Although the entire universe may be much larger than our observable universe,we can see only within our observable universe.The "boundary" of our observable universe is called

What is the best way to determine a galaxy's redshift?

Although it is difficult to tell from our vantage point inside the galaxy,astronomers suspect that the Milky Way is a barred spiral.

Why are Cepheid variables important?

Why are galaxies in the blue cloud blue?

Which statement below correctly describes the relationship between expansion rate and age for the universe?

Which of the following is not one of the three major categories of galaxies?

The most basic difference between elliptical galaxies and spiral galaxies is that

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