Exam 16: A Universe of Galaxies

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A larger value for the Hubble's constant...

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The observational evidence that quasars ...

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A) Black holes form first, seeding the formation of galaxies.
B) All galaxies start out as spiral galaxies.
C) Galaxies form first, then black holes.
D) Some regions in the universe start out denser than others.

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A) He measured the parallaxes of the Cepheids in Andromeda to determine their distances. He showed that Andromeda was far outside the Milky Way Galaxy.
B) As a Cepheid is a type of luminous galaxy, Hubble's discovery of Cepheids in Andromeda proved that it was a separate galaxy from the Milky Way.
C) From the period- luminosity relation for Cepheids, he was able to determine the distance to Andromeda. He showed that it was far outside the Milky Way Galaxy.
D) There are no Cepheids in the Milky Way, so his discovery proved that Andromeda had to be in another galaxy.
E) He used main- sequence fitting to determine the distances to the Cepheids. He showed that Andromeda was far outside the Milky Way Galaxy.

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A) They are often spiral galaxies.
B) They often have multiple galactic nuclei near their centers.
C) They are thought to form by the merger of several smaller galaxies.
D) They're found in clusters of galaxies.

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A) Beyond the cosmological horizon, we would be looking back to a time before the universe was born.
B) Every galaxy in the entire universe (not just the observable universe) exists within the cosmological horizon, so there's nothing to see beyond it.
C) The cosmological horizon is infinitely far away, and we can't see to infinity.
D) We do not have big enough telescopes.

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A) The universe started out filled almost uniformly with hydrogen and helium.
B) Gas contracted to form the disks of galaxies before any stars were born.
C) The universe is expanding.
D) Some regions in the universe were slightly more dense than others.

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A) a very large luminosity compared to the total luminosity of the Milky Way
B) a rate of star formation that may be 100 or more times greater than that in the Milky Way
C) strong radio emission from "lobes" of material well outside the visible boundaries of the galaxy
D) the presence of an unusually large number of binary star systems containing X- ray bursters

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A) Sam
B) Molly
C) They both would measure the same age.

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A) The more distant the galaxy, the redder it is, but there are some exceptions.
B) The more distant the galaxy, the bluer it is, but there are some exceptions.
C) There is no trend because there are some exceptions.

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A) They are very bright, so they can be used to determine the distances to galaxies billions of light- years away.
B) They should all have approximately the same luminosity.
C) We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately.
D) They occur so frequently that we can use them to measure the distances to virtually all galaxies.
E) both A and B

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A) 3 solar masses
B) 1 billion solar masses
C) 1 trillion solar masses
D) 10 solar masses

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A) the radiating away of thermal energy
B) the formation of the first generation of stars
C) the shock waves from the exploding supernovae of the earliest stars
D) the pull of gravity of the mass of the cloud material
E) the conversion of gravitational potential energy into kinetic and thermal energy as the cloud collapsed

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A) a pecan nut about 1 centimeter away
B) a grapefruit about 1 kilometer away
C) a compact disk about the length of a football field away
D) a grapefruit a few meters away
E) a compact disk a few meters away

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A) 10 million years
B) 10 billion years
C) 4 1/2 billion years
D) 14 billion years

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A) any object with an extremely large redshift
B) an active galactic nucleus that is particularly bright
C) a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster
D) a galaxy with an unusually high rate of star formation

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A) Stars shine with energy generated by nuclear fusion in their cores.
B) More distant galaxies are moving away from us faster than nearby galaxies.
C) Stars can shine brightly for millions of years.
D) All planets orbit the Sun in the same direction and in nearly the same plane.

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