Question 1

If the distance of a galaxy is 50 Mpc, what is its recessional velocity if the Hubble constant is assumed to be 70 km/s/Mpc?

Accepted Answer

A)  700 km/s 
B)  1,000 km/s 
C)  3,500 km/s 
D)  5,000 km/s 
E)  7,000 km/s 
A)  700 km/s 
B)  1,000 km/s 
C)  3,500 km/s 
D)  5,000 km/s 
E)  7,000 km/s C

Question 2

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

Question 3

The light curve of a Cepheid variable star allows astronomers to infer its mean brightness of 1.9 x10-14 W/m2 and the period of pulsation about 4.8 days.Utilizing the calibrated relation between period and luminosity for Classical Cepheids, its luminosity is estimated to be 8.3 x1029 W.What is the distance to that Cepheid star and, implicitly, the distance to its host galaxy?

Accepted Answer

Using the equation relating brightness,luminosity,and distance:   Given the relatively short distance,we could guess this is a Cepheid hosted by a satellite galaxy of our Milky Way.

Question 4

Quasars are most likely to be found

Accepted Answer

A)  near our galaxy. 
B)  in the centers of elliptical galaxies. 
C)  at extreme distances. 
D)  in very old galaxies. 
E)  in dwarf galaxies. 
A)  near our galaxy. 
B)  in the centers of elliptical galaxies. 
C)  at extreme distances. 
D)  in very old galaxies. 
E)  in dwarf galaxies.

Question 5

In the figure shown below, the upper spectrum is from hydrogen at rest in a laboratory, and the lower spectrum is from a galaxy.How far away is this galaxy?

Accepted Answer

A)  110 Mpc 
B)  170 Mpc 
C)  230 Mpc 
D)  280 Mpc 
E)  340 Mpc 
A)  110 Mpc 
B)  170 Mpc 
C)  230 Mpc 
D)  280 Mpc 
E)  340 Mpc

Question 6

The nearest big galaxy, Andromeda, is at an estimated distance of

Accepted Answer

A)  780 Mpc. 
B)  0.78 kpc. 
C)  0.78 Mpc. 
D)  25 kpc. 
E)  250 Gpc. 
A)  780 Mpc. 
B)  0.78 kpc. 
C)  0.78 Mpc. 
D)  25 kpc. 
E)  250 Gpc.

Question 7

Would you expect life to be more likely (or common) in a spiral galaxy or in an elliptical galaxy? Justify your reasoning with relevant properties from each type of galaxy.

Accepted Answer

Elliptical galaxies have mostly older st

Question 8

In most cases it is impossible to observe the host galaxies of quasars because

Accepted Answer

A)  quasars outshine the host galaxies by a few orders of magnitude. 
B)  the supermassive black holes have "eaten" all the stars in those galaxies. 
C)  the host galaxies of quasars have too much dark matter. 
D)  the host galaxies of quasars have too much obscuring dust. 
E)  the galaxies hosting quasars are much smaller than our own Milky Way. 
A)  quasars outshine the host galaxies by a few orders of magnitude. 
B)  the supermassive black holes have "eaten" all the stars in those galaxies. 
C)  the host galaxies of quasars have too much dark matter. 
D)  the host galaxies of quasars have too much obscuring dust. 
E)  the galaxies hosting quasars are much smaller than our own Milky Way.

Question 9

How do we know that the stellar disks in spiral galaxies are flat? How do we know that elliptical galaxies are not flat?

Accepted Answer

Individual galaxies are oriented at a va

Question 10

How have astronomers searched for evidence of MACHOs in the halo of the Milky Way?

Accepted Answer

A)  They search for stars that are binary companions of MACHOs. 
B)  They search for rapidly moving massive gas clouds. 
C)  They search for disturbances in the background of gravitational waves. 
D)  They search for distant stars with light briefly amplified by gravitational lensing. 
E)  They search for close binary stars undergoing mass transfer. 
A)  They search for stars that are binary companions of MACHOs. 
B)  They search for rapidly moving massive gas clouds. 
C)  They search for disturbances in the background of gravitational waves. 
D)  They search for distant stars with light briefly amplified by gravitational lensing. 
E)  They search for close binary stars undergoing mass transfer.

Question 11

In some radio galaxies, we see only one side of the jet because

Accepted Answer

A)  the black hole produces a jet in only one direction. 
B)  of relativistic beaming. 
C)  the other side is inside the black hole's event horizon. 
D)  of dust obscuration. 
E)  of dark matter that blocks the light from one side of the jet. 
A)  the black hole produces a jet in only one direction. 
B)  of relativistic beaming. 
C)  the other side is inside the black hole's event horizon. 
D)  of dust obscuration. 
E)  of dark matter that blocks the light from one side of the jet.

Question 12

Why do the light gray bands (labeled Radar, Parallax, etc.) that cover certain ranges of distances in the figure shown below overlap with one another both at the beginning and at the end?

Accepted Answer

The overlapping portions of th

Question 13

In the Great Debate of 1920, Curtis and Shapley argued over whether or not

Accepted Answer

A)  the Big Bang occurred. 
B)  the age of the universe was 14 billion years. 
C)  the universe was contracting. 
D)  life existed outside Earth. 
E)  the spiral nebulae were located outside the Milky Way. 
A)  the Big Bang occurred. 
B)  the age of the universe was 14 billion years. 
C)  the universe was contracting. 
D)  life existed outside Earth. 
E)  the spiral nebulae were located outside the Milky Way.

Question 14

What happens to active galaxies when their AGNs run out of fuel?

Accepted Answer

A)  The black holes powering them collapse even further. 
B)  They simply become normal galaxies. 
C)  They slowly dissipate into clouds of gas and dust. 
D)  They eventually pull in material from farther out, starting the AGN process all over again. 
E)  They explode as gamma-ray bursts. 
A)  The black holes powering them collapse even further. 
B)  They simply become normal galaxies. 
C)  They slowly dissipate into clouds of gas and dust. 
D)  They eventually pull in material from farther out, starting the AGN process all over again. 
E)  They explode as gamma-ray bursts.

Question 15

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

Accepted Answer

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

Question 16

Order the following objects by the maximum distance from which they can be detected: Cepheid variables, RR Lyrae stars, Type Ia supernovae, and low-mass main-sequence stars.Explain your reasoning.

Accepted Answer

Objects can be seen at farther distances

Question 17

Quasars remain unresolved sources, even with the best telescopic observations, because they

Accepted Answer

A)  are too luminous. 
B)  occupy a very small volume. 
C)  are quite blue. 
D)  produce copious amounts of radio energy. 
E)  host supermassive black holes. 
A)  are too luminous. 
B)  occupy a very small volume. 
C)  are quite blue. 
D)  produce copious amounts of radio energy. 
E)  host supermassive black holes.

Question 18

AGNs are most likely powered by

Accepted Answer

A)  extremely dense star clusters. 
B)  accreting supermassive black holes. 
C)  ultradense molecular clouds. 
D)  decaying dark matter. 
E)  supernova explosions. 
A)  extremely dense star clusters. 
B)  accreting supermassive black holes. 
C)  ultradense molecular clouds. 
D)  decaying dark matter. 
E)  supernova explosions.

Question 19

The rotation curve of a galaxy 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. 
E)  ages of star clusters. 
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. 
E)  ages of star clusters.

Question 20

The disks of spiral galaxies appear blue because

Accepted Answer

A)  they are moving toward us. 
B)  they contain a relatively high concentration of low-mass stars. 
C)  they contain active regions of star formation. 
D)  they contain more metals that, when ionized, emit blue light. 
E)  stars collide with each other frequently in these dense regions and explode as Type Ia supernovae. 
A)  they are moving toward us. 
B)  they contain a relatively high concentration of low-mass stars. 
C)  they contain active regions of star formation. 
D)  they contain more metals that, when ionized, emit blue light. 
E)  stars collide with each other frequently in these dense regions and explode as Type Ia supernovae.

Exam 19: Galaxies

If the distance of a galaxy is 50 Mpc, what is its recessional velocity if the Hubble constant is assumed to be 70 km/s/Mpc?

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

Quasars are most likely to be found

In the figure shown below, the upper spectrum is from hydrogen at rest in a laboratory, and the lower spectrum is from a galaxy.How far away is this galaxy?

The nearest big galaxy, Andromeda, is at an estimated distance of

Would you expect life to be more likely (or common) in a spiral galaxy or in an elliptical galaxy? Justify your reasoning with relevant properties from each type of galaxy.

In most cases it is impossible to observe the host galaxies of quasars because

How do we know that the stellar disks in spiral galaxies are flat? How do we know that elliptical galaxies are not flat?

How have astronomers searched for evidence of MACHOs in the halo of the Milky Way?

In some radio galaxies, we see only one side of the jet because

Why do the light gray bands (labeled Radar, Parallax, etc.) that cover certain ranges of distances in the figure shown below overlap with one another both at the beginning and at the end?

In the Great Debate of 1920, Curtis and Shapley argued over whether or not

What happens to active galaxies when their AGNs run out of fuel?

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

Order the following objects by the maximum distance from which they can be detected: Cepheid variables, RR Lyrae stars, Type Ia supernovae, and low-mass main-sequence stars.Explain your reasoning.

Quasars remain unresolved sources, even with the best telescopic observations, because they

AGNs are most likely powered by

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

The disks of spiral galaxies appear blue because

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