Question 1

___________ have elongated nuclei with spiral structure extending from the ends of the elongations. The Milky Way is a member of this class of galaxy.
A) Spiral galaxies
B) Barred spiral galaxies
C) Elliptical galaxies
D) Irregular galaxies
E) S0 galaxies

Accepted Answer

B

Question 2

The total mass of galaxies in a cluster of galaxies divided by the number of galaxies in the cluster can be used to determine a typical galaxy's ___________.
A) luminosity
B) distance
C) mass
D) diameter
E) age

Accepted Answer

The total mass of galaxies in a cluster of galaxies divided by the number of galaxies in the cluster gives us the average mass of a galaxy in that cluster. Therefore, the correct answer would be C) mass.

Question 3

The look-back time is
A) the time it takes for the light from an object to reach Earth.
B) numerically equal to the distance in light-years.
C) smaller for more distant objects.
D) All of the other choices are correct.
E) the time it takes for the light from an object to reach Earth and numerically equal to the distance in light-years.

Accepted Answer

The look-back time is defined as the time it takes for the light from an object to reach Earth. This is also numerically equal to the distance in light-years because the speed of light is constant. Therefore, choice E is the best answer. Choice A is partially correct but does not include the numerical equivalence to distance. Choice B is only true because of the constant speed of light. Choice C is incorrect because larger distances correspond to larger look-back times. Choice D is incorrect because not all of the choices are correct.

Question 4

___________ are produced when two galaxies pass near each other and pull large streamers of stars, gas, and dust away from the galaxies.
A) Ring galaxies
B) Spiral galaxies
C) Rotation curves
D) Tidal tails
E) Irregular galaxies

Accepted Answer

Tidal tails are produced when two galaxies pass near each other and pull large streamers of stars, gas, and dust away from the galaxies. Ring galaxies are caused by a head-on collision between two galaxies, while spiral galaxies have distinctive spiral arms. Rotation curves are graphs showing the motion of objects within a galaxy, and irregular galaxies have no definite shape or structure.

Question 5

Astronomers now speculate that a galaxy's shape depends on all of the following except
A) the rate of star formation.
B) the history of past collisions.
C) the mass.
D) All of the other choices may be important in determining a galaxy's shape.

Accepted Answer

All of the other choices may play a role in determining a galaxy's shape.

Question 6

The Milky Way is part of
I. a poor cluster.
II. a rich cluster.
III. the Virgo Cluster.
IV. the Local Group.
A) I and III
B) I and IV
C) II and III
D) II and IV
E) just III

Accepted Answer

The Milky Way is not part of a rich cluster like choice II and it is not part of the Virgo Cluster as a whole but rather part of the Local Group, which includes the Andromeda Galaxy and smaller galaxies. Therefore, choices I and III are incorrect. The correct choices are I and IV, as the Milky Way is part of a poor cluster called the Local Group.

Question 7

The Hubble law is a relation between a galaxy's
A) mass and its luminosity.
B) distance and its luminosity.
C) mass and its recession velocity.
D) distance and its recession velocity.
E) mass and its diameter.

Accepted Answer

The Hubble law states that a galaxy's recession velocity is directly proportional to its distance. This means that as the distance between Earth and a galaxy increases, the speed at which the galaxy moves away from us also increases. Therefore, the correct choice is D, "distance and its recession velocity."

Question 8

Poor clusters
A) contain more than 1000 stars and are found in the halo of the galaxy.
B) contain lots of young stars and are found in the disk of a spiral galaxy.
C) contain more than 1000 galaxies and are generally elliptical in shape.
D) contain fewer than 1000 galaxies and tend to be irregularly shaped.
E) are found in the nucleus of the galaxy.

Accepted Answer

Poor clusters contain fewer than 1000 galaxies and are characterized by their irregular shapes, distinguishing them from rich clusters which are more densely populated and have a more defined structure.

Question 9

The rotation curve of a galaxy can be used to determine
A) the relative number of hot young stars in the galaxy.
B) the relative amount of gas and dust in the galaxy.
C) the radius of the galaxy.
D) the luminosity of the galaxy.
E) the mass of the galaxy.

Accepted Answer

The rotation curve of a galaxy can be used to determine the mass of the galaxy. This is because the observed velocity of stars and gas in the galaxy is determined by the gravitational pull of all the mass within the galaxy. Therefore, by studying the rotation curve of a galaxy, astronomers can determine the mass of the galaxy, including both visible matter (stars, gas, dust) and dark matter.

Question 10

Most of the mass of a galaxy is contained in the
A) massive O and B stars in the galaxy.
B) H I regions of the galaxy.
C) H II regions of the galaxy.
D) dark matter of the galaxy.
E) disk of the galaxy.

Accepted Answer

Dark matter is a hypothetical form of matter that does not emit, absorb or reflect light, making it invisible to telescopes. However, its gravitational effects can be observed, and it is believed to make up most of the mass in galaxies.

Question 11

A ___________ generally contains well over 1000 galaxies and is quite dense. They often contain many giant elliptical galaxies.
A) local group
B) poor cluster
C) rich cluster
D) tidal tail
E) quasar

Accepted Answer

A rich cluster is a cluster of galaxies that contains a large number of galaxies, often over 1000, and is quite dense. They are known to contain many giant elliptical galaxies. The other options are not descriptive of a rich cluster.

Question 12

__________ can be used to determine the galaxy's mass if the galaxy is reasonably close, so that the Doppler shift of the galaxy disk material can be measured at several distances from the galaxy's center relative to the center.
A) The Hubble constant
B) A galaxy's color
C) A galaxy's rotation curve
D) A galaxy's diameter
E) The velocity dispersion method

Accepted Answer

The rotation curve of a galaxy can be used to determine its mass by measuring the Doppler shift of the galaxy disk material at several distances from the galaxy's center relative to the center. This method is known as the Rotation Curve Method.

Question 13

Gravitational lensing
A) occurs when light passes near a massive object and is deflected by the object's gravitational field.
B) can be used to determine the luminosity of a galaxy.
C) occurs when the mass of a galaxy is greater than expected from the luminosity of the galaxy.
D) occurs when the mass of a galaxy is less than expected from the luminosity of the galaxy.
E) can be used to determine the recessional velocity of a galaxy.

Accepted Answer

Gravitational lensing occurs when light passes near a massive object and is deflected by the object's gravitational field.

Question 14

We should expect galaxies to collide fairly often because
A) they are large with respect to their separation distances.
B) galaxies contain large amounts of neutral hydrogen.
C) galaxies occur in clusters.
D) they are large with respect to their separation distances and galaxies occur in clusters.
E) None of the other choices are correct.

Accepted Answer

Galaxies are large with respect to their separation distances and they occur in clusters, increasing the likelihood of collisions.

Question 15

Mathematical models indicate that ___________ galaxies are produced by high-speed collisions in which a smaller galaxy passes through another galaxy almost perpendicular to the disk of the galaxy.
A) ring
B) spiral
C) antenna
D) irregular
E) tidal tail

Accepted Answer

Ring galaxies are formed as a result of high-speed collisions where a smaller galaxy passes almost perpendicular through the disk of a larger galaxy, creating a ring-like structure.

Question 16

A megaparsec is equivalent to
A) 3.26 light-years.
B) 206,265 AU.
C) the age of our solar system.
D) a million parsecs.
E) the diameter of the Milky Way galaxy.

Accepted Answer

A megaparsec is a unit of distance in astronomy that is equal to one million parsecs. A parsec is approximately 3.26 light-years, so a megaparsec represents a much larger distance than the other options suggest.

Question 17

___________ galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.
A) Irregular
B) S0
C) E7
D) Sa
E) E0

Accepted Answer

Irregular galaxies have no definite structure or shape, and are characterized by their random appearance. They often contain large amounts of gas and dust, as well as young and old stars, but lack the spiral arms and nucleus commonly found in other types of galaxies.

Question 18

A mega-parsec (Mpc) is equivalent to
A) 3.26 light-years.
B) 206,265 light years.
C) 1,000,000 light years
D) 3,260,000 light-years.
E) the diameter of the Milky Way galaxy.

Accepted Answer

A mega-parsec (Mpc) is equivalent to approximately 3.26 million light-years, making option D correct.

Question 19

The mass of a single galaxy might be found by
A) the double galaxy method.
B) the rotation curve method.
C) the cluster method.
D) any of the methods (i.e., double galaxy, rotation curve, cluster)
E) none of these methods.

Accepted Answer

The rotation curve method involves measuring the distribution of mass within a galaxy by observing the rotation velocity of stars and gas around the galaxy's center. By analyzing the rotation curve, astronomers can determine the mass of the galaxy. This method is considered to be one of the most reliable ways of measuring the mass of a single galaxy. The double galaxy method and the cluster method are used to determine the masses of groups of galaxies, while none of these methods provide accurate measurements of the mass of a single galaxy.

Question 20

Galactic cannibalism refers to
A) binary galaxies.
B) the merging of galaxies.
C) galaxies drawing in gas from the intergalactic medium.
D) the destruction of a galaxy's globular clusters by the galaxy's nucleus.
E) None of the other choices are correct.

Accepted Answer

Galactic cannibalism refers to the merging of galaxies, where one galaxy devours another or they both merge together. This process can lead to the formation of larger galaxies and the disruption of the smaller galaxies.

Quiz 13: Galaxies: Normal and Active

___________ have elongated nuclei with spiral structure extending from the ends of the elongations. The Milky Way is a member of this class of galaxy.

The total mass of galaxies in a cluster of galaxies divided by the number of galaxies in the cluster can be used to determine a typical galaxy's ___________.

The look-back time is

___________ are produced when two galaxies pass near each other and pull large streamers of stars, gas, and dust away from the galaxies.

Astronomers now speculate that a galaxy's shape depends on all of the following except

The Milky Way is part of I. a poor cluster. II. a rich cluster. III. the Virgo Cluster. IV. the Local Group.

The Hubble law is a relation between a galaxy's

Poor clusters

The rotation curve of a galaxy can be used to determine

Most of the mass of a galaxy is contained in the

A ___________ generally contains well over 1000 galaxies and is quite dense. They often contain many giant elliptical galaxies.

__________ can be used to determine the galaxy's mass if the galaxy is reasonably close, so that the Doppler shift of the galaxy disk material can be measured at several distances from the galaxy's center relative to the center.

Gravitational lensing

We should expect galaxies to collide fairly often because

Mathematical models indicate that ___________ galaxies are produced by high-speed collisions in which a smaller galaxy passes through another galaxy almost perpendicular to the disk of the galaxy.

A megaparsec is equivalent to

___________ galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.

A mega-parsec (Mpc) is equivalent to

The mass of a single galaxy might be found by

Galactic cannibalism refers to