Exam 15: The Realm of the Galaxies

Correct Answer

verified

Because there curren...

View Answer

Show Answer

A) The velocity of stars rises dramatically at large distances from the centers of galaxies,implying large amounts of dark matter cause these stars to move much faster than stars at smaller distances.
B) The velocity of stars stays somewhat constant at distances beyond the visible edges of galaxies,implying that more matter than what we observe in stars and gas must be there.
C) The velocity of stars is low in the inner regions of galaxies,suggesting that dark matter is impeding their motion.
D) The velocity of stars rises quickly in the inner regions of galaxies,suggesting that unseen matter is gravitationally moving this material at faster rates than expected.

Correct Answer

verified

Show Answer

A) the black hole only produces a jet in one direction
B) of relativistic beaming
C) the other side is inside the black hole's event horizon
D) of dust obscuration

Correct Answer

verified

Show Answer

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

Correct Answer

verified

Show Answer

A) Hydrogen emission from H II regions in the spiral disk
B) The velocities of satellite dwarf galaxies surrounding a spiral galaxy
C) Absorption lines in the spectra of its globular clusters
D) all of the above

Correct Answer

verified

D

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 primarily hidden by large amounts of cold gas and dust

Correct Answer

verified

Show Answer

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

Correct Answer

verified

Show Answer

A) A central supermassive black hole
B) Dark matter
C) Massive O- and B-type stars
D) Cold molecular gas clouds

Correct Answer

verified

B

A) rotates at the same speed as the gas in the disk
B) rotates at a speed that is different than the gas in the disk
C) stays constant in time as the gas in the disk rotates through it
D) none of the above is true

Correct Answer

verified

Show Answer

A) v $\propto$ r^-1/2
B) v $\propto$ r²
C) v $\propto$ r^-1
D) v $\propto$ r

Correct Answer

verified

Show 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

Correct Answer

verified

Show Answer

A) Rotation curve A
B) Rotation curve B
C) Rotation curve C
D) None of the curves would be correct.

Correct Answer

verified

Show Answer

Correct Answer

verified

Show 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.

Correct Answer

verified

Show Answer

Correct Answer

verified

Show 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.

Correct Answer

verified

Show Answer

A) rotate too fast
B) contain little molecular hydrogen
C) are too massive
D) are too far away

Correct Answer

verified

B

Correct Answer

verified

The radius of the gas is r = 26,000 ly =...

View Answer

Show Answer