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Astronomy
A BEGINNER’S GUIDE
TO THE UNIVERSE
EIGHTH EDITION
CHAPTER 16
Galaxies and Dark Matter
Clickers
© 2017 Pearson Education, Inc.
Question 1
Based on galactic rotation curves and motions in clusters
of galaxies, dark matter
a) makes up about 90 percent of the
matter in the universe.
b) is best detected by the largest optical
telescopes.
c) makes up about 10 percent of the
matter in clusters of galaxies.
d) exists but has no observable effects
on galaxies.
e) is the result of gas and dust.
© 2017 Pearson Education, Inc.
Question 1
Based on galactic rotation curves and motions in clusters
of galaxies, dark matter
a) makes up about 90 percent of the
matter in the universe.
b) is best detected by the largest optical
telescopes.
c) makes up about 10 percent of the
matter in clusters of galaxies.
d) exists but has no observable effects
on galaxies.
e) is the result of gas and dust.
© 2017 Pearson Education, Inc.
Question 2
Collisions between galaxies
a)
b)
c)
d)
are much rarer than collisions between stars.
can transform elliptical galaxies into spirals.
trigger Type II supernova explosions in the halo.
cause gas and dust clouds to collide, leading to
rapid star formation.
© 2017 Pearson Education, Inc.
Question 2
Collisions between galaxies
a)
b)
c)
d)
are much rarer than collisions between stars.
can transform elliptical galaxies into spirals.
trigger Type II supernova explosions in the halo.
cause gas and dust clouds to collide, leading to
rapid star formation.
Explanation: Galaxies are
relatively close compared
with their size. In clusters of
galaxies, collisions clearly
occur.
© 2017 Pearson Education, Inc.
Question 3
When spiral galaxies collide, the greatest impact occurs
on their
a)
b)
c)
d)
e)
globular cluster stars.
giant molecular clouds.
central bulge stars.
open clusters.
disk stars.
© 2017 Pearson Education, Inc.
Question 3
When spiral galaxies collide, the greatest impact occurs
on their
a)
b)
c)
d)
e)
globular cluster stars.
giant molecular clouds.
central bulge stars.
open clusters.
disk stars.
© 2017 Pearson Education, Inc.
Question 4
Due to the density and collisions among galaxies, _____
are rare in the centers of clusters.
a)
b)
c)
d)
e)
giant ellipticals
irregulars
spirals
active galaxies
radio galaxies
© 2017 Pearson Education, Inc.
Question 4
Due to the density and collisions among galaxies, _____
are rare in the centers of clusters.
a)
b)
c)
d)
e)
giant ellipticals
irregulars
spirals
active galaxies
radio galaxies
Explanation: The gas, dust, and disks of spiral galaxies
are tidally disrupted, and even destroyed, in the centers of dense
clusters, which are often dominated by giant elliptical galaxies.
© 2017 Pearson Education, Inc.
Question 5
The rapid variation of brightness of quasars indicates
a)
b)
c)
d)
e)
the source of energy is very small.
energy is coming from matter and antimatter.
the energy source is rotating rapidly.
a chain reaction of supernovas occurs.
there are many separate sources of energy in the core.
© 2017 Pearson Education, Inc.
Question 5
The rapid variation of brightness of quasars indicates
a)
b)
c)
d)
e)
the source of energy is very small.
energy is coming from matter and antimatter.
the energy source is rotating rapidly.
a chain reaction of supernovas occurs.
there are many separate sources of energy in the core.
Explanation: The size of
an object cannot be
larger than the distance
light can travel in the
time it takes to change
its brightness.
© 2017 Pearson Education, Inc.
Question 6
A galaxy seen 1 billion light-years away means we see it
as it
a)
b)
c)
d)
e)
was when the universe was 1 billion years old.
will be 1 billion years from now.
was 1 billion years ago.
is today, but redshifted 10 percent of the speed of light.
was just after the Big Bang.
© 2017 Pearson Education, Inc.
Question 6
A galaxy seen 1 billion light-years away means we see it
as it
a)
b)
c)
d)
was when the universe was 1 billion years old.
will be 1 billion years from now.
was 1 billion years ago.
is today, but redshifted 10
percent of the speed of light.
e) was just after the Big Bang.
Explanation: Looking farther away
in space means looking back further
in time, to when the object (and
universe) was younger.
© 2017 Pearson Education, Inc.
Question 7
The large-scale distribution of galaxies in the universe
reveals
a) a smooth, continuous, and homogeneous
arrangement of clusters.
b) large voids, with most of the galaxies lying in
filaments and sheets.
c) a large supercluster at the center of the universe.
d) a central void with walls of galaxies at the edge of
the universe.
© 2017 Pearson Education, Inc.
Question 7
The large-scale distribution of galaxies in the universe
reveals
a) a smooth, continuous, and homogeneous
arrangement of clusters.
b) large voids, with most
of the galaxies lying in
filaments and sheets.
c) a large supercluster at
the center of the universe.
d) a central void with walls of
galaxies at the edge of the
universe.
© 2017 Pearson Education, Inc.
Question 8
The lensing of a distant quasar is produced in a foreground
galaxy by its
a)
b)
c)
d)
e)
total mass of stars, gas, and dark matter.
central supermassive black hole.
globular clusters.
magnetic fields.
intergalactic gas.
© 2017 Pearson Education, Inc.
Question 8
The lensing of a distant quasar is produced in a foreground
galaxy by its
a)
b)
c)
d)
e)
total mass of stars, gas, and dark matter.
central supermassive black hole.
globular clusters.
magnetic fields.
intergalactic gas.
Explanation: The twin quasar
AC114 has two images of the
same object.
© 2017 Pearson Education, Inc.
Question 9
The blue arcs in this image are
a)
b)
c)
d)
emission nebulae.
nearby blue dwarf galaxies.
blue supergiant stars.
a very distant galaxy imaged
by a massive galaxy cluster
between us and the distant
galaxy.
© 2017 Pearson Education, Inc.
Question 9
The blue arcs in this image are
a)
b)
c)
d)
emission nebulae.
nearby blue dwarf galaxies.
blue supergiant stars.
a very distant galaxy imaged
by a massive galaxy cluster
between us and the distant
galaxy.
Explanation: The nearby galaxy—yellow blobs in the center of this
image—is 1.5 billion pc from us. The blue arcs are all images of a
single, much more distant galaxy.
© 2017 Pearson Education, Inc.