Question 1

Using the figure below, estimate for this galaxy the ratio of dark matter mass to total mass
contained within a radius of 100 kpc.

Accepted Answer

At a radius of 100 kpc,the amo

Question 2

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

Accepted Answer

A)  5-10 percent 
B)  25-30 percent 
C)  40-50 percent 
D)  70-75 percent 
E)  90-95 percent 
A)  5-10 percent 
B)  25-30 percent 
C)  40-50 percent 
D)  70-75 percent 
E)  90-95 percent

Question 3

Why can Type Ia supernovae be used to determine a galaxy's distance?

Accepted Answer

A)  Type Ia supernovae occur only in very luminous galaxies. 
B)  Most Type Ia supernovae have approximately the same peak luminosity. 
C)  Most Type Ia supernovae have approximately the same size. 
D)  A Type Ia supernova occurs in a typical galaxy about once every 100 years. 
E)  Type Ia supernovae occur even in very small galaxies. 
A)  Type Ia supernovae occur only in very luminous galaxies. 
B)  Most Type Ia supernovae have approximately the same peak luminosity. 
C)  Most Type Ia supernovae have approximately the same size. 
D)  A Type Ia supernova occurs in a typical galaxy about once every 100 years. 
E)  Type Ia supernovae occur even in very small galaxies.

Question 4

If you found a galaxy with an H$\alpha$ emission line that had a wavelength of 756.3 nm, what would be the galaxy's distance if the Hubble constant is 70 km/s/Mpc? (Note that the rest wavelength of the H$\alpha$ emission line is 656.3 nm.)

Accepted Answer

A)  650 Mpc 
B)  760 Mpc 
C)  3,200 Mpc 
D)  6,400 Mpc 
E)  7,600 Mpc 
A)  650 Mpc 
B)  760 Mpc 
C)  3,200 Mpc 
D)  6,400 Mpc 
E)  7,600 Mpc

Question 5

Astronomers have known that galaxies are separate entities outside of our own for roughly the last

Accepted Answer

A)  35 years. 
B)  60 years. 
C)  90 years. 
D)  150 years. 
E)  210 years. 
A)  35 years. 
B)  60 years. 
C)  90 years. 
D)  150 years. 
E)  210 years.

Question 6

How can we measure the mass of an elliptical galaxy?

Accepted Answer

A)  by measuring the speeds of stars in the nucleus 
B)  by observing the velocity of the hot, X-ray-emitting gas that surrounds the galaxy 
C)  by measuring the number of H II regions in the galaxy 
D)  by measuring how many supernovae go off each century 
E)  by measuring the amount of blue light in the galaxy 
A)  by measuring the speeds of stars in the nucleus 
B)  by observing the velocity of the hot, X-ray-emitting gas that surrounds the galaxy 
C)  by measuring the number of H II regions in the galaxy 
D)  by measuring how many supernovae go off each century 
E)  by measuring the amount of blue light in the galaxy

Question 7

Which of the following images shows an edge-on spiral galaxy?

Accepted Answer

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

Question 8

The Hubble classification scheme for galaxies sorts them by their

Accepted Answer

A)  evolutionary state. 
B)  mass. 
C)  amount of dust. 
D)  amount of dark matter. 
E)  visual appearance. 
A)  evolutionary state. 
B)  mass. 
C)  amount of dust. 
D)  amount of dark matter. 
E)  visual appearance.

Question 9

Assume that when a supermassive black hole accretes gas, approximately 20 percent of the accreted mass is converted directly into energy, which is radiated away.If a quasar has a luminosity of 1013 LSUN, then what must be its mass accretion rate? Note that the Sun has a luminosity of 4 x1026 W, and a mass of 2 x1030 kg.

Accepted Answer

A)  1 MSUN per year 
B)  3.5 MSUN per year 
C)  1 MSUN per century 
D)  3.5 MSUN per century 
E)  1 MSUN per million years 
A)  1 MSUN per year 
B)  3.5 MSUN per year 
C)  1 MSUN per century 
D)  3.5 MSUN per century 
E)  1 MSUN per million years

Question 10

What do the broad emission lines in quasar spectra tell astronomers about these objects?

Accepted Answer

A)  They are very far away. 
B)  They are moving away from us. 
C)  They have rapid internal motions. 
D)  They are very dense. 
E)  They have few heavy elements. 
A)  They are very far away. 
B)  They are moving away from us. 
C)  They have rapid internal motions. 
D)  They are very dense. 
E)  They have few heavy elements.

Question 11

Name three types of active galactic nuclei and give at least one reason why each is unique.

Accepted Answer

Three types of AGNs: (1)quasars-extremel

Question 12

Stars in the disks of spiral galaxies have orbits that are

Accepted Answer

A)  randomly oriented. 
B)  constantly getting larger. 
C)  mostly aligned in the same plane. 
D)  spiral-shaped. 
E)  unaffected by dark matter. 
A)  randomly oriented. 
B)  constantly getting larger. 
C)  mostly aligned in the same plane. 
D)  spiral-shaped. 
E)  unaffected by dark matter.

Question 13

A certain spectral line of rest wavelength lrest (i.e., laboratory value) is shifted by 100 nm in a quasar.A second line from the same quasar with a rest wavelength half the (rest) value of the first one would be shifted by

Accepted Answer

A)  200 nm. 
B)  100 nm. 
C)  500 nm. 
D)  50 nm. 
E)  1000 nm. 
A)  200 nm. 
B)  100 nm. 
C)  500 nm. 
D)  50 nm. 
E)  1000 nm.

Question 14

How does the appearance of an AGN depend on the viewing angle to the nucleus?

Accepted Answer

An AGN of any type (e.g.,Seyferts or qua

Question 15

You observe a reddish galaxy with stars that orbit in random directions.This galaxy is most likely a(n)

Accepted Answer

A)  elliptical galaxy. 
B)  unbarred spiral galaxy. 
C)  irregular galaxy. 
D)  barred spiral. 
E)  It is none of these; more information is needed. 
A)  elliptical galaxy. 
B)  unbarred spiral galaxy. 
C)  irregular galaxy. 
D)  barred spiral. 
E)  It is none of these; more information is needed.

Question 16

How do we explain that "billions of galaxies are closer to Earth than the nearest quasar"?

Accepted Answer

A large fraction of billions of galaxies

Question 17

If you measure the velocity of a cloud of gas that is rotating around the center of a galaxy in a circular orbit with radius R, you can determine the

Accepted Answer

A)  total mass of the galaxy. 
B)  mass of the stars and gas in the galaxy. 
C)  mass of the galaxy enclosed within the radius R. 
D)  mass of the galaxy located outside the radius R. 
E)  mass of luminous matter within the radius R. 
A)  total mass of the galaxy. 
B)  mass of the stars and gas in the galaxy. 
C)  mass of the galaxy enclosed within the radius R. 
D)  mass of the galaxy located outside the radius R. 
E)  mass of luminous matter within the radius R.

Question 18

If a Seyfert galaxy's nucleus varies in brightness on the timescale of 10 hours, then what is the approximate upper limit for the size of the emitting region?

Accepted Answer

A)  20 AU 
B)  30 AU 
C)  50 AU 
D)  70 AU 
E)  120 AU 
A)  20 AU 
B)  30 AU 
C)  50 AU 
D)  70 AU 
E)  120 AU

Question 19

Which of the following functions correctly illustrates the relation between mean density and black hole mass?

Accepted Answer

A)  ($\rho$   M  - 2 ) 
B)  ($\rho$  M  - 1 ) 
C)  ($\rho$    ) 
D)  ($\rho$  M ) 
E)  ($\rho$  M  2) 
A)  ($\rho$   M  - 2 ) 
B)  ($\rho$  M  - 1 ) 
C)  ($\rho$    ) 
D)  ($\rho$  M ) 
E)  ($\rho$  M  2)

Question 20

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

Accepted Answer

The (upper limit)size of the AGN is the

Exam 19: Galaxies

Using the figure below, estimate for this galaxy the ratio of dark matter mass to total mass contained within a radius of 100 kpc.

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

Why can Type Ia supernovae be used to determine a galaxy's distance?

If you found a galaxy with an H α\alphaα emission line that had a wavelength of 756.3 nm, what would be the galaxy's distance if the Hubble constant is 70 km/s/Mpc? (Note that the rest wavelength of the H α\alphaα emission line is 656.3 nm.)

Astronomers have known that galaxies are separate entities outside of our own for roughly the last

How can we measure the mass of an elliptical galaxy?

Which of the following images shows an edge-on spiral galaxy?

The Hubble classification scheme for galaxies sorts them by their

What do the broad emission lines in quasar spectra tell astronomers about these objects?

Name three types of active galactic nuclei and give at least one reason why each is unique.

Stars in the disks of spiral galaxies have orbits that are

A certain spectral line of rest wavelength lrest (i.e., laboratory value) is shifted by 100 nm in a quasar.A second line from the same quasar with a rest wavelength half the (rest) value of the first one would be shifted by

How does the appearance of an AGN depend on the viewing angle to the nucleus?

You observe a reddish galaxy with stars that orbit in random directions.This galaxy is most likely a(n)

How do we explain that "billions of galaxies are closer to Earth than the nearest quasar"?

If you measure the velocity of a cloud of gas that is rotating around the center of a galaxy in a circular orbit with radius R, you can determine the

If a Seyfert galaxy's nucleus varies in brightness on the timescale of 10 hours, then what is the approximate upper limit for the size of the emitting region?

Which of the following functions correctly illustrates the relation between mean density and black hole mass?

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

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Cosmology

Large-Scale Structure in the Universe

Life

Filters

If you found a galaxy with an H $\alpha$ emission line that had a wavelength of 756.3 nm, what would be the galaxy's distance if the Hubble constant is 70 km/s/Mpc? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)

A certain spectral line of rest wavelength l_rest(i.e., laboratory value) is shifted by 100 nm in a quasar.A second line from the same quasar with a rest wavelength half the (rest) value of the first one would be shifted by