Question 1

If there is a 4 million MSUN black hole at the center of our galaxy, why is our own galaxy not an AGN?

Accepted Answer

There is currently no significant infall...

Question 2

We interpret the presence of more AGNs in the past than today to indicate that

Accepted Answer

A)   there were fewer galaxy-galaxy interactions in the past.
B)   there were more galaxy-galaxy interactions in the past.
C)   supermassive black holes were larger in the past.
D)   today's AGNs are hidden primarily by large amounts of cold gas and dust.
E)   AGNs had bigger central black holes in the past.

Question 3

What were the positions taken by Heber Curtis and Harlow Shapley in their "Great Debate," and how were both of them partially correct?

Accepted Answer

Curtis believed in a smaller galaxy (rou...

Question 4

Dust in galaxies does not count as dark matter because

Accepted Answer

A)   it absorbs only some wavelengths of light but not all wavelengths as dark matter does.
B)   it interacts with light.
C)   it is found only in spiral disks, whereas dark matter is also found in elliptical galaxies.
D)   dust is easily destroyed by dark matter.
E)   there is never enough to account for all the gravity in galaxies.

Question 5

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.
E)   presence of an active nucleus.

Question 6

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

Accepted Answer

Spirals contain lots of dust and cold ga...

Question 7

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

Accepted Answer

A)   They measured the velocities of stars in the inner regions of 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.
E)   They measured the X-ray emission from hot gas gravitationally bound to the galaxies.

Question 8

The spectra of most galaxies tell us that

Accepted Answer

A)   galaxies appear to be moving away from us.
B)   their light comes predominantly from objects other than stars.
C)   most galaxies contain clouds of gas that are absorbing their favorite wavelengths.
D)   galaxies in the past rotated at a faster rate than they do today.
E)   galaxies are rushing through space in all directions.

Question 9

Quasars were first discovered in which region of the electromagnetic spectrum?

Accepted Answer

A)   X-ray
B)   gamma-ray
C)   radio
D)   infrared
E)   visible

Question 10

For the more distant quasars, the emission lines that would normally occur in the visible domain would be shifted into

Accepted Answer

A)   UV.
B)   X-rays.
C)   gamma rays.
D)   infrared.
E)   radio.

Question 11

Describe the known properties of dark matter, and contrast it with "normal" matter.

Accepted Answer

Our main evidence for dark matter comes ...

Question 12

The Tully-Fisher method of determination of distances to galaxies is based on the correlation between

Accepted Answer

A)   color and redshift.
B)   star formation rate and morphological type.
C)   width of emission lines and black hole accretion rate.
D)   rotational speed and luminosity.
E)   dark matter radial profile and X-ray brightness.

Question 13

Dark matter is most likely made up of

Accepted Answer

A)   elementary particles that have mass but do not interact much with normal matter.
B)   supermassive black holes.
C)   faint stellar remnants such as white dwarfs and neutron stars.
D)   free-floating Jupiter-mass planets.
E)   cold concentrations of dust.

Question 14

The nearest known quasar shows a redshift of z = 0.0516, which means it is at a distance of

Accepted Answer

A)   220 Mpc.
B)   450 Mpc.
C)   100 Mpc.
D)   15,400 Mpc.
E)   100 kpc.

Question 15

Type Ia supernovae have a peak luminosity of 3.7 x1036 W.If you discover a Type Ia supernovae in a distant galaxy that has a measured brightness of 9.5 x10-17 W/m2, then how far away is this galaxy? Note that 1 Mpc = 3.1 x1022 m.

Accepted Answer

A)   0.3 Mpc
B)   40 Mpc
C)   1,200 Mpc
D)   1,800 Mpc
E)   3,500 Mpc

Question 16

You see a galaxy in which the H α\alphaα  line (rest wavelength = 656.3 nm)  is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line that has a rest wavelength of 1,083 nm?

Accepted Answer

A)   1,083 nm
B)   1,183 nm
C)   1,248 nm
D)   1,440 nm
E)   3,142 nm

Question 17

Microquasars are scaled-down versions of quasars, the former being powered by accretion onto stellar-sized black holes, the material being provided by a companion star.The underlying mechanism seems to be very similar in both microquasars and their supermassive AGNs.Typical microquasars have luminosities that are ten orders of magnitude lower than ordinary quasars.What is the typical level of accretion rate in the two cases?

Accepted Answer

Microquasars have luminosities 10<sup>10...

Question 18

If a galaxy has a recessional velocity of 50,000 km/s, at what wavelength will you observe the H α\alphaα  emission line? (Note that the rest wavelength of the H α\alphaα  emission line is 656.3 nm.)

Accepted Answer

A)   695.7 nm
B)   719.4 nm
C)   742.3 nm
D)   765.7 nm
E)   1,750 nm

Question 19

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 redshift? (Note that the rest wavelength of the H α\alphaα  emission line is 656.3 nm.)

Accepted Answer

A)   0.05
B)   0.07
C)   0.10
D)   0.13
E)   0.15

Question 20

What type of galaxy is shown in the figure below?

Accepted Answer

A)   a giant elliptical
B)   an ordinary spiral galaxy
C)   an irregular galaxy
D)   a barred spiral
E)   a dwarf elliptical

Exam 19: Galaxies

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

Correct Answer
verified
Spirals contain lots of dust and cold ga...
View Answer

The spectra of most galaxies tell us that

Correct Answer
verified

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

Correct Answer
verified

Dark matter is most likely made up of

Correct Answer
verified

What type of galaxy is shown in the figure below?

Correct Answer
verified

For the more distant quasars, the emission lines that would normally occur in the visible domain would be shifted into

Correct Answer
verified

Dust in galaxies does not count as dark matter because

Correct Answer
verified

We interpret the presence of more AGNs in the past than today to indicate that

Correct Answer
verified

The Tully-Fisher method of determination of distances to galaxies is based on the correlation between

Correct Answer
verified

The nearest known quasar shows a redshift of z = 0.0516, which means it is at a distance of

Correct Answer
verified

If a galaxy has a recessional velocity of 50,000 km/s, at what wavelength will you observe the H $\alpha$ emission line? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)

Correct Answer
verified

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 redshift? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)

Correct Answer
verified

Correct Answer
verified
Microquasars have luminosities 10^10...
View Answer

What were the positions taken by Heber Curtis and Harlow Shapley in their "Great Debate," and how were both of them partially correct?

Correct Answer
verified
Curtis believed in a smaller galaxy (rou...
View Answer

You see a galaxy in which the H $\alpha$ line (rest wavelength = 656.3 nm) is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line that has a rest wavelength of 1,083 nm?

Correct Answer
verified

Type Ia supernovae have a peak luminosity of 3.7 x10³⁶ W.If you discover a Type Ia supernovae in a distant galaxy that has a measured brightness of 9.5 x10^-17 W/m², then how far away is this galaxy? Note that 1 Mpc = 3.1 x10²² m.

Correct Answer
verified

Describe the known properties of dark matter, and contrast it with "normal" matter.

Correct Answer
verified
Our main evidence for dark matter comes ...
View Answer

Quasars were first discovered in which region of the electromagnetic spectrum?

Correct Answer
verified

If there is a 4 million M_SUN black hole at the center of our galaxy, why is our own galaxy not an AGN?

Correct Answer
verified
There is currently no significant infall...
View Answer

In spiral galaxies, the size of the central bulge is correlated with the

Correct Answer
verified

Exam 19: Galaxies

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

Correct AnswerverifiedSpirals contain lots of dust and cold ga...View AnswerShow Answer

The spectra of most galaxies tell us that

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Dark matter is most likely made up of

Correct AnswerverifiedShow Answer

What type of galaxy is shown in the figure below?

Correct AnswerverifiedShow Answer

For the more distant quasars, the emission lines that would normally occur in the visible domain would be shifted into

Correct AnswerverifiedShow Answer

Dust in galaxies does not count as dark matter because

Correct AnswerverifiedShow Answer

We interpret the presence of more AGNs in the past than today to indicate that

Correct AnswerverifiedShow Answer

The Tully-Fisher method of determination of distances to galaxies is based on the correlation between

Correct AnswerverifiedShow Answer

The nearest known quasar shows a redshift of z = 0.0516, which means it is at a distance of

Correct AnswerverifiedShow Answer

If a galaxy has a recessional velocity of 50,000 km/s, at what wavelength will you observe the H α\alphaα emission line? (Note that the rest wavelength of the H α\alphaα emission line is 656.3 nm.)

Correct AnswerverifiedShow Answer

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 redshift? (Note that the rest wavelength of the H α\alphaα emission line is 656.3 nm.)

Correct AnswerverifiedShow Answer

Correct AnswerverifiedMicroquasars have luminosities 1010...View AnswerShow Answer

What were the positions taken by Heber Curtis and Harlow Shapley in their "Great Debate," and how were both of them partially correct?

Correct AnswerverifiedCurtis believed in a smaller galaxy (rou...View AnswerShow Answer

You see a galaxy in which the H α\alphaα line (rest wavelength = 656.3 nm) is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line that has a rest wavelength of 1,083 nm?

Correct AnswerverifiedShow Answer

Type Ia supernovae have a peak luminosity of 3.7 x1036 W.If you discover a Type Ia supernovae in a distant galaxy that has a measured brightness of 9.5 x10-17 W/m2, then how far away is this galaxy? Note that 1 Mpc = 3.1 x1022 m.

Correct AnswerverifiedShow Answer

Describe the known properties of dark matter, and contrast it with "normal" matter.

Correct AnswerverifiedOur main evidence for dark matter comes ...View AnswerShow Answer

Quasars were first discovered in which region of the electromagnetic spectrum?

Correct AnswerverifiedShow Answer

If there is a 4 million MSUN black hole at the center of our galaxy, why is our own galaxy not an AGN?

Correct AnswerverifiedThere is currently no significant infall...View AnswerShow Answer

In spiral galaxies, the size of the central bulge is correlated with the

Correct AnswerverifiedShow Answer

Correct Answer
verified
Spirals contain lots of dust and cold ga...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

If a galaxy has a recessional velocity of 50,000 km/s, at what wavelength will you observe the H $\alpha$ emission line? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)

Correct Answer
verified

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 redshift? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)

Correct Answer
verified

Correct Answer
verified
Microquasars have luminosities 10^10...
View Answer

Correct Answer
verified
Curtis believed in a smaller galaxy (rou...
View Answer

You see a galaxy in which the H $\alpha$ line (rest wavelength = 656.3 nm) is observed at a wavelength of 756.3 nm.What would be the observed wavelength of a particular helium line that has a rest wavelength of 1,083 nm?

Correct Answer
verified

Type Ia supernovae have a peak luminosity of 3.7 x10³⁶ W.If you discover a Type Ia supernovae in a distant galaxy that has a measured brightness of 9.5 x10^-17 W/m², then how far away is this galaxy? Note that 1 Mpc = 3.1 x10²² m.

Correct Answer
verified

Correct Answer
verified
Our main evidence for dark matter comes ...
View Answer

Correct Answer
verified

If there is a 4 million M_SUN black hole at the center of our galaxy, why is our own galaxy not an AGN?

Correct Answer
verified
There is currently no significant infall...
View Answer

Correct Answer
verified