Question 1

The disks of spiral galaxies appear blue because:

Accepted Answer

A)   spiral galaxies are moving toward us
B)   spiral galaxies contain mostly hot blue stars
C)   spiral galaxies are still undergoing star formation
D)   spiral galaxies contain more metals that,when ionized,emit blue light

Question 2

Assume that when a supermassive black hole accretes gas,approximately 50 percent of its mass is converted directly into energy,which is radiated away.If a quasar has a luminosity of 1014 L ⊙\odot⊙  then what must its mass accretion rate be?

Accepted Answer

A)   1 M  ⊙\odot⊙   per year
B)   10 M ⊙\odot⊙   per year
C)   1 M ⊙\odot⊙   per century
D)   10 M ⊙\odot⊙  per million years

Question 3

How do astronomers know that AGNs are as small as our Solar System?

Accepted Answer

AGNs have been observed to vary dramatic...

Question 4

The figure below shows the unified model of AGNs along with three observers.Which observer would have the least ability to see detail in the object?

Accepted Answer

A)   Observer A
B)   Observer B
C)   Observer C
D)   All observers can equally see detail in the object.

Question 5

Describe two ways by which spiral structure may be induced in a spiral galaxy's disk.

Accepted Answer

Possibilities are: (1)gravitational inte...

Question 6

Roughly what percentage of the total mass of a galaxy is made up of luminous,or normal,matter?

Accepted Answer

A)   5 percent
B)   25 percent
C)   50 percent
D)   90 percent

Question 7

If the rotational speed of the gas in the disk of a spiral galaxy is 200 km/s at a distance of 80,000 light-years from its center,then what is the mass enclosed within this radius?

Accepted Answer

A)   7.5 billion M ⊙\odot⊙  
B)   18 billion M ⊙\odot⊙  
C)   70 billion M ⊙\odot⊙  
D)   230 billion M ⊙\odot⊙

Question 8

What is the connection between active galaxies and galactic mergers?

Accepted Answer

Astronomers believe that galactic merger...

Question 9

How did astronomers determine that elliptical galaxies are composed mostly of dark matter?

Accepted Answer

A)   They measured X-ray emission from hot gas gravitationally bound to the galaxies.
B)   They measured the rotation rates of gas as a function of distance from the centers of the galaxies.
C)   They measured the amount of gravitational pull elliptical galaxies have on companion galaxies.
D)   They assumed that the proportion of dark matter was roughly the same as in spiral galaxies.

Question 10

In the search for MACHOs,which meter in the figure below would register the brightest value?

Accepted Answer

A)   Brightness meter A
B)   Brightness meter B
C)   Brightness meter C
D)   All of them would register the same brightness

Question 11

Which of the following are NOT predominantly found in the spiral arms of galaxies?

Accepted Answer

A)   Molecular clouds
B)   H II regions
C)   K- and M-type stars
D)   Type II supernovae

Question 12

Star formation in spiral galaxies happens only in the spiral arms.

Accepted Answer

A) True 
 B)False

Question 13

Dark matter is distributed inside galaxies in exactly the same way as luminous matter,although the total mass of dark matter is much larger than that of luminous matter.

Accepted Answer

A) True 
 B)False

Question 14

If the radio lobes of a radio galaxy extend out to 10 Mpc from the center of the galaxy and the particles in them are traveling at approximately 0.99 c,then how long must the black hole at the center have been ejecting this material into space? Note that 1 Mpc = 3.1 × 1022 m and 1 year = 3 × 107 s.

Accepted Answer

Because v = d/t,the length of ...

Question 15

How do we know that AGN have sizes on the order of our Solar System?

Accepted Answer

A)   Quasars and Seyfert galaxies are stellar-like sources.
B)   Their brightness varies by factors of a few.
C)   The emission lines in their spectra show gas rotating at speeds of thousands of km/s.
D)   Their brightness varies on timescales of hours to a day.

Question 16

How do the current star formation rates of spiral and elliptical galaxies compare?

Accepted Answer

Spirals contain lots of cold gas in thei...

Question 17

More luminous giant galaxies tend to have __________ supermassive black holes at their centers.

Accepted Answer

A)   more massive
B)   radio quiet
C)   more luminous
D)   slower rotating

Question 18

The image below is of a spiral galaxy.  In spiral galaxies,the size of the central bulge is correlated with the:

Accepted Answer

A)   tightness of the spiral arms
B)   luminosity of the galaxy
C)   age of the galaxy
D)   thickness of the disk

Question 19

Galaxies that are classified as quasars were much more numerous in the past.

Accepted Answer

A) True 
 B)False

Question 20

How did Hubble use his tuning fork diagram (figure below)to classify galaxies? Is there any significance to this organization?

Accepted Answer

Elliptical and spiral galaxies are organ...

Exam 15: The Realm of the Galaxies

Star formation in spiral galaxies happens only in the spiral arms.

Correct Answer
verified

How do astronomers know that AGNs are as small as our Solar System?

Correct Answer
verified
AGNs have been observed to vary dramatic...
View Answer

Dark matter is distributed inside galaxies in exactly the same way as luminous matter,although the total mass of dark matter is much larger than that of luminous matter.

Correct Answer
verified

The image below is of a spiral galaxy. In spiral galaxies,the size of the central bulge is correlated with the:

Correct Answer
verified

The figure below shows the unified model of AGNs along with three observers.Which observer would have the least ability to see detail in the object?

Correct Answer
verified

More luminous giant galaxies tend to have __________ supermassive black holes at their centers.

Correct Answer
verified

How do the current star formation rates of spiral and elliptical galaxies compare?

Correct Answer
verified
Spirals contain lots of cold gas in thei...
View Answer

How did Hubble use his tuning fork diagram (figure below)to classify galaxies? Is there any significance to this organization?

Correct Answer
verified
Elliptical and spiral galaxies are organ...
View Answer

If the rotational speed of the gas in the disk of a spiral galaxy is 200 km/s at a distance of 80,000 light-years from its center,then what is the mass enclosed within this radius?

Correct Answer
verified

How did astronomers determine that elliptical galaxies are composed mostly of dark matter?

Correct Answer
verified

Roughly what percentage of the total mass of a galaxy is made up of luminous,or normal,matter?

Correct Answer
verified

Which of the following are NOT predominantly found in the spiral arms of galaxies?

Correct Answer
verified

How do we know that AGN have sizes on the order of our Solar System?

Correct Answer
verified

Assume that when a supermassive black hole accretes gas,approximately 50 percent of its mass is converted directly into energy,which is radiated away.If a quasar has a luminosity of 10¹⁴ L_$\odot$then what must its mass accretion rate be?

Correct Answer
verified

The disks of spiral galaxies appear blue because:

Correct Answer
verified

Describe two ways by which spiral structure may be induced in a spiral galaxy's disk.

Correct Answer
verified
Possibilities are: (1)gravitational inte...
View Answer

Galaxies that are classified as quasars were much more numerous in the past.

Correct Answer
verified

What is the connection between active galaxies and galactic mergers?

Correct Answer
verified
Astronomers believe that galactic merger...
View Answer

Correct Answer
verified
Because v = d/t,the length of ...
View Answer

In the search for MACHOs,which meter in the figure below would register the brightest value?

Correct Answer
verified

Exam 15: The Realm of the Galaxies

Star formation in spiral galaxies happens only in the spiral arms.

Correct AnswerverifiedShow Answer

How do astronomers know that AGNs are as small as our Solar System?

Correct AnswerverifiedAGNs have been observed to vary dramatic...View AnswerShow Answer

Dark matter is distributed inside galaxies in exactly the same way as luminous matter,although the total mass of dark matter is much larger than that of luminous matter.

Correct AnswerverifiedShow Answer

The image below is of a spiral galaxy. In spiral galaxies,the size of the central bulge is correlated with the:

Correct AnswerverifiedShow Answer

The figure below shows the unified model of AGNs along with three observers.Which observer would have the least ability to see detail in the object?

Correct AnswerverifiedShow Answer

More luminous giant galaxies tend to have __________ supermassive black holes at their centers.

Correct AnswerverifiedShow Answer

How do the current star formation rates of spiral and elliptical galaxies compare?

Correct AnswerverifiedSpirals contain lots of cold gas in thei...View AnswerShow Answer

How did Hubble use his tuning fork diagram (figure below)to classify galaxies? Is there any significance to this organization?

Correct AnswerverifiedElliptical and spiral galaxies are organ...View AnswerShow Answer

If the rotational speed of the gas in the disk of a spiral galaxy is 200 km/s at a distance of 80,000 light-years from its center,then what is the mass enclosed within this radius?

Correct AnswerverifiedShow Answer

How did astronomers determine that elliptical galaxies are composed mostly of dark matter?

Correct AnswerverifiedShow Answer

Roughly what percentage of the total mass of a galaxy is made up of luminous,or normal,matter?

Correct AnswerverifiedShow Answer

Which of the following are NOT predominantly found in the spiral arms of galaxies?

Correct AnswerverifiedShow Answer

How do we know that AGN have sizes on the order of our Solar System?

Correct AnswerverifiedShow Answer

Assume that when a supermassive black hole accretes gas,approximately 50 percent of its mass is converted directly into energy,which is radiated away.If a quasar has a luminosity of 1014 L ⊙\odot⊙ then what must its mass accretion rate be?

Correct AnswerverifiedShow Answer

The disks of spiral galaxies appear blue because:

Correct AnswerverifiedShow Answer

Describe two ways by which spiral structure may be induced in a spiral galaxy's disk.

Correct AnswerverifiedPossibilities are: (1)gravitational inte...View AnswerShow Answer

Galaxies that are classified as quasars were much more numerous in the past.

Correct AnswerverifiedShow Answer

What is the connection between active galaxies and galactic mergers?

Correct AnswerverifiedAstronomers believe that galactic merger...View AnswerShow Answer

Correct AnswerverifiedBecause v = d/t,the length of ...View AnswerShow Answer

In the search for MACHOs,which meter in the figure below would register the brightest value?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified
AGNs have been observed to vary dramatic...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Spirals contain lots of cold gas in thei...
View Answer

Correct Answer
verified
Elliptical and spiral galaxies are organ...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Assume that when a supermassive black hole accretes gas,approximately 50 percent of its mass is converted directly into energy,which is radiated away.If a quasar has a luminosity of 10¹⁴ L_$\odot$then what must its mass accretion rate be?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Possibilities are: (1)gravitational inte...
View Answer

Correct Answer
verified

Correct Answer
verified
Astronomers believe that galactic merger...
View Answer

Correct Answer
verified
Because v = d/t,the length of ...
View Answer

Correct Answer
verified