Question 1

Any asymmetry in the gravity field of a spiral galaxy can induce spiral structure.

Accepted Answer

A) True 
 B)False

Question 2

Spiral structure can be triggered in a disk galaxy by

Accepted Answer

A)  a close encounter with a passing galaxy. 
B)  an orbiting dwarf galaxy. 
C)  an off-center burst of star formation in the disk. 
D)  All of the above 
A)  a close encounter with a passing galaxy. 
B)  an orbiting dwarf galaxy. 
C)  an off-center burst of star formation in the disk. 
D)  All of the above

Question 3

The observed redshifts of quasars tell us all of the following EXCEPT

Accepted Answer

A)  quasars are extremely luminous. 
B)  quasars are rare in the universe today. 
C)  quasars are incredibly far from us. 
D)  quasars are extremely massive. 
A)  quasars are extremely luminous. 
B)  quasars are rare in the universe today. 
C)  quasars are incredibly far from us. 
D)  quasars are extremely massive.

Question 4

If the rotational speed of the gas in the disk of a spiral galaxy is 100 km/s at a distance of 26,000 light-years from its center,then what is the mass enclosed within this radius? If the mass of luminous matter inside this radius is 5 billion   then what fraction of the galaxy's mass is made of dark matter?

Accepted Answer

The radius of the gas is @#IMG-DLM& and

Question 5

If an AGN varies its brightness on a timescale of 4 hours,then what is the size of the AGN measured in AU?

Accepted Answer

The size of the AGN is the dis

Question 6

Although elliptical and irregular galaxies have been observed in both dwarf and giant varieties,we find only giant spiral galaxies.

Accepted Answer

A) True 
 B)False

Question 7

What is the approximate percentage of nearby galaxies that contain AGN?

Accepted Answer

A)  3 percent 
B)  15 percent 
C)  40 percent 
D)  80 percent 
A)  3 percent 
B)  15 percent 
C)  40 percent 
D)  80 percent

Question 8

What is a rotation curve,and what can it tell us about a galaxy?

Accepted Answer

A rotation curve is a plot of the veloci

Question 9

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   then what must its mass accretion rate be?

Accepted Answer

A)    per year 
B)    per year 
C)    per century 
D)    per million years 
A)    per year 
B)    per year 
C)    per century 
D)    per million years

Question 10

If a galaxy had no dark matter,how would the velocity (v)of a star that orbited far outside the visible extent of the galaxy depend on its distance (r)from the center of the galaxy?

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

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

Question 12

Today only 30 percent of galaxies are AGN.

Accepted Answer

A) True 
 B)False

Question 13

What do the formation of the Solar System and the existence of AGNs have in common?

Accepted Answer

A)  They both demonstrate the importance of how luminosity varies with time. 
B)  They both demonstrate the high efficiency of nuclear fusion. 
C)  They both demonstrate the importance of accretion disks. 
D)  They both demonstrate the importance of living in the center of a galaxy. 
A)  They both demonstrate the importance of how luminosity varies with time. 
B)  They both demonstrate the high efficiency of nuclear fusion. 
C)  They both demonstrate the importance of accretion disks. 
D)  They both demonstrate the importance of living in the center of a galaxy.

Question 14

The unified model of AGN suggests that quasars,Seyfert galaxies,and radio galaxies

Accepted Answer

A)  are similar phenomena but viewed from different orientation angles. 
B)  are powered by similar mass accretion rates onto supermassive black holes. 
C)  are driven by violent mergers of two gas-rich spiral galaxies. 
D)  are unrelated,although they are all very luminous galaxies at radio wavelengths. 
A)  are similar phenomena but viewed from different orientation angles. 
B)  are powered by similar mass accretion rates onto supermassive black holes. 
C)  are driven by violent mergers of two gas-rich spiral galaxies. 
D)  are unrelated,although they are all very luminous galaxies at radio wavelengths.

Question 15

Approximately __________ of spiral galaxies are barred.

Accepted Answer

A)  10 percent 
B)  25 percent 
C)  50 percent 
D)  75 percent 
A)  10 percent 
B)  25 percent 
C)  50 percent 
D)  75 percent

Question 16

Long-lasting spiral density waves occur in the disk of a spiral galaxy when

Accepted Answer

A)  the spiral merges with another galaxy. 
B)  the galaxy is too close. 
C)  the galaxy's disk is regularly disturbed. 
D)  None of the above 
A)  the spiral merges with another galaxy. 
B)  the galaxy is too close. 
C)  the galaxy's disk is regularly disturbed. 
D)  None of the above

Question 17

A galaxy rotation curve is a plot of the rotation speed as a function of the

Accepted Answer

A)  galaxy's luminosity. 
B)  mass of the dark matter halo. 
C)  brightness of the luminous matter in the galaxy. 
D)  radius from the center. 
A)  galaxy's luminosity. 
B)  mass of the dark matter halo. 
C)  brightness of the luminous matter in the galaxy. 
D)  radius from the center.

Question 18

We classify galaxies by

Accepted Answer

A)  their true shapes. 
B)  how they appear in the sky. 
C)  the amount of gas and dust in them. 
D)  whether they are near or far from us. 
A)  their true shapes. 
B)  how they appear in the sky. 
C)  the amount of gas and dust in them. 
D)  whether they are near or far from us.

Question 19

Why is 21-cm radiation a good spiral arm tracer?

Accepted Answer

A)  Emitted by neutral hydrogen,it traces the location of concentrations of gas. 
B)  Emitted by O and B stars,it traces the location of newly formed stars. 
C)  Emitted by ionized hydrogen,it traces the location of H II regions. 
D)  Emitted by molecular hydrogen,it traces the location of clouds in the process of collapsing into stars. 
A)  Emitted by neutral hydrogen,it traces the location of concentrations of gas. 
B)  Emitted by O and B stars,it traces the location of newly formed stars. 
C)  Emitted by ionized hydrogen,it traces the location of H II regions. 
D)  Emitted by molecular hydrogen,it traces the location of clouds in the process of collapsing into stars.

Question 20

The dark matter in galaxies is __________ the luminous material.

Accepted Answer

A)  distributed in roughly the same way as 
B)  much more extended in radius than 
C)  much more centrally concentrated than 
D)  much less uniform in density than 
A)  distributed in roughly the same way as 
B)  much more extended in radius than 
C)  much more centrally concentrated than 
D)  much less uniform in density than

Exam 19: Galaxies

Any asymmetry in the gravity field of a spiral galaxy can induce spiral structure.

Spiral structure can be triggered in a disk galaxy by

The observed redshifts of quasars tell us all of the following EXCEPT

If an AGN varies its brightness on a timescale of 4 hours,then what is the size of the AGN measured in AU?

Although elliptical and irregular galaxies have been observed in both dwarf and giant varieties,we find only giant spiral galaxies.

What is the approximate percentage of nearby galaxies that contain AGN?

What is a rotation curve,and what can it tell us about a galaxy?

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 then what must its mass accretion rate be?

If a galaxy had no dark matter,how would the velocity (v)of a star that orbited far outside the visible extent of the galaxy depend on its distance (r)from the center of the galaxy?

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

Today only 30 percent of galaxies are AGN.

What do the formation of the Solar System and the existence of AGNs have in common?

The unified model of AGN suggests that quasars,Seyfert galaxies,and radio galaxies

Approximately __________ of spiral galaxies are barred.

Long-lasting spiral density waves occur in the disk of a spiral galaxy when

A galaxy rotation curve is a plot of the rotation speed as a function of the

We classify galaxies by

Why is 21-cm radiation a good spiral arm tracer?

The dark matter in galaxies is __________ the luminous material.

Why Learn Astronomy

Patterns in the Skymotions of Earth

Gravity and Orbitsa Celestial Ballet

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Gravity Is More Than Keplers Laws

Planetary Adornmentsmoons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

A Run-Of-The-Mill G-Type Starour Sun

Star Formation and the Interstellar Medium

Stars in the Slow Lanelow-Mass Stellar Evolution

Live Fast,die Younghigh-Mass Stellar Evolution

Our Expanding Universe

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

The Origin of Structure

Life

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