Transcript The unusually bright centers found in some galaxies are called

February 9, 2013
@ 11:00 am
The unusually bright centers found in some
galaxies are called
1. active galactic
nuclei.
2. starbursts.
3. halos.
4. supermassive black
holes.
40
17
2
1
2
0
3
4
According to current understanding, what is a
quasar?
1. An active galactic nucleus
that is particularly bright.
2. Any object with an
extremely large redshift.
3. A galaxy with an unusually
high rate of star formation.
4. A very large galaxy thought
to be formed by the
merger of several smaller
galaxies, typically found in
the center of a galaxy
cluster.
42
14
1
1
2
3
3
4
The luminosity of a quasar is generated in a
region the size of
1.
2.
3.
4.
the Milky Way.
a star cluster.
the solar system.
a planet.
30
21
6
2
1
2
3
4
The observed relationship between the masses of central black
holes and the bulge masses of galaxies implies that
1. the black holes will
eventually suck in the rest
of the galaxy.
2. the biggest galaxies have
the most luminous quasars.
3. quasars were more
common 10 billion years
ago than they are today.
4. galaxy formation and
supermassive black holes
formation must be related
somehow.
49
5
7
0
1
2
3
4
The best evidence for the existence of
supermassive black holes is
1.
2.
3.
4.
large quantities of high-energy
emission, such as X-rays and
gamma rays, and radio emission
from relativistic electrons.
jet velocities that approach the
speed of light.
huge dark regions in the centers
of galaxies, where black holes
have been sucking in the galaxy
from the inside out.
very high orbital velocities in a
very compact region.
25
19
10
7
1
2
3
4
A quasar’s spectrum is hugely redshifted. What do most
astronomers think this large redshift tells us about the quasar?
1. The size of the quasar’s
central supermassive black
hole.
2. The type of host galaxy in
which the quasar resides.
3. The composition of the
quasar.
4. The distance to the quasar.
47
7
3
1
2
2
3
4
Most active galactic nuclei are found at large distances from us,
with relatively few nearby. What does this imply?
1.
2.
3.
4.
Supermassive black holes
existed only when the universe
was young, and no longer exist
today.
The jets seen in many active
galactic nuclei must cause them
to move far away from us.
Active galactic nuclei tend to
become less active as they age.
Active galactic nuclei can form
only at large distances from the
Milky Way.
43
6
9
2
1
2
3
4