21.Based the galaxies found in the Local Group of galaxies, : 1777264
21.Based on the galaxies found in the Local Group of galaxies, the most common type of galaxy in the universe is expected to be
A.the spiral galaxies.
B.the barred spiral galaxies.
C.the dwarf elliptical galaxies.
D.the irregular galaxies.
E.the giant elliptical galaxies.
22.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.a and c
E.none of the above
23.__________ galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.
24.___________ is an irregular galaxy that is passing close to the Milky Way and is expected to merge with the Milky Way in the future.
A.The Andromeda galaxy
B.The Small Magellanic Cloud
D.The Virgo cluster
E.The Whirlpool galaxy
25.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.
26.The Milky Way galaxy is part of
A.the Virgo cluster.
B.the Large Magellanic Cloud.
C.the Small Magellanic Cloud.
D.the Local Group.
E.a rich cluster.
27.It is believed that ring galaxies form
A.when two galaxies collide nearly head on at high speed.
B.when two spiral galaxies collide, but not directly head on.
C.from a large cloud of gas and dust with very little angular momentum.
D.from a large cloud of gas and dust with a very high angular momentum.
E.when more than two galaxies collide at the same time.
28.Observations of galaxies and clusters of galaxies indicate that about ____ percent of the matteruniverse is dark matter.
A.contain a large number of very young stars, but very little evidence of gas clouds.
B.contain a large number of very old stars and almost no gas or dust.
C.are often associated with a galaxy that is colliding with another galaxy.
D.are common in rich clusters.
E.are composed of filaments and voids.
30.An elliptical galaxy could
A.evolve into an irregular galaxy when it has used up all of its gas and dust.
B.be formed from the collision and merger of spiral galaxies.
C.evolve from a single spiral galaxy when the spiral has used up all of its gas and dust.
D.become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster.
E.evolve from an S0 galaxy if the S0 galaxy were to increase its rotation rate.