Exam 15: Galaxies and the Foundation of Modern Cosmology

A) 2.5 x 10⁹ (2.5 billion) light years.
B) 4 x 10⁹ (4 billion) light years.
C) 1 x 10⁹ (1 billion) light years.
D) It is impossible to say since there are exceptions.

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A) The stars in the halo of the Milky Way are organized into several dense clusters arranged throughout the halo.
B) The Milky Way resembles an elliptical galaxy more than other spirals do.
C) Halo stars differ in age and heavy-element content, but these variations do not seem to depend on the stars' distance from the galactic center.
D) The bulge of the Milky Way is surrounded by many globular clusters, just as elliptical galaxies are.
E) The Milky Way is the central galaxy of a dense cluster of galaxies.

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A) The observed features that cause us to classify it as a "starburst" must be only temporary phenomena in the galaxy's history.
B) Its rate of star formation is many times higher than the rate of star formation in the Milky Way.
C) Supernovae occur so frequently that their effects combine to drive a galactic wind that blows material into intergalactic space.
D) The observed features of the starburst are thought to be caused by the presence of a supermassive black hole in the galaxy's center.

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A) Dr. X believes that the universe is expanding, but Dr. Y does not.
B) Dr. X believes that the Andromeda Galaxy (a member of our Local Group) is moving away from us at a slower speed than Dr. Y believes.
C) Dr. X believes that the universe is older than Dr. Y believes.
D) Dr. X believes that the universe will someday stop expanding, while Dr. Y believes it will expand forever.
E) Dr. X believes that the universe has a much higher density than Dr. Y believes.

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A) an object for which we are likely to know its true luminosity
B) an object for which we can easily measure its apparent brightness
C) a class of objects that we know all have exactly the same luminosity
D) any star for which we know its exact apparent brightness
E) a unit of luminosity used by astronomers

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A) The period between its peaks of brightness and its luminosity
B) The period between its peaks of brightness and its distance
C) Its luminosity and its mass
D) Its mass and its distance

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A) the high speeds at which galaxies move within clusters
B) the expansion of the universe
C) very old, red stars in distant galaxies
D) supermassive black holes

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A) There are no Cepheids in the Milky Way, so his discovery proved that Andromeda had to be in another galaxy.
B) He measured the parallaxes of the Cepheids in Andromeda to determine their distances. He showed that Andromeda was far outside the Milky Way Galaxy.
C) He used main-sequence fitting to determine the distances to the Cepheids. He showed that Andromeda was far outside the Milky Way Galaxy.
D) 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.
E) 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.

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D

A) the light from the galaxy as it is today, and it is blueshifted
B) the light from the galaxy as it is today, and it is redshifted
C) the light from the galaxy as it was 100 million years ago, and it is blueshifted
D) the light from the galaxy as it was 100 million years ago, and it is redshifted
E) Nothing: the galaxy lies beyond the cosmological horizon.

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A) observations of some elliptical galaxies surrounded by shells of stars that probably formed from stars stripped out of smaller galaxies
B) the fact that elliptical galaxies dominate the galaxy populations at the cores of dense clusters of galaxies
C) observations of some elliptical galaxies with stars and gas clouds in their cores that orbit differently from the other stars in the galaxy
D) observations of giant elliptical galaxies at the center of dense clusters that may have grown by consuming other galaxies
E) all of the above

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A) halo
B) bulge
C) spiral arms
D) globular clusters
E) all of the above

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A) the one that is reddest in color
B) the one that is bluest in color
C) the one that is farthest away
D) the one that is closest to us
E) the one that appears smallest in size

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A) Some may have all exploded as supernovae by now.
B) Some may have formed in large clusters.
C) Some may have formed singly, in isolation from one another.
D) Some may still exist in the Milky Way today.
E) Some may have had rocky planets around them.

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E

A) White dwarf supernovae all have roughly the same true peak luminosity, while massive supernovae come in a wide range of peak luminosities.
B) We can see only white dwarf supernovae in distant galaxies, not massive star supernovae.
C) White dwarf supernovae are much more common than massive star supernovae.
D) White dwarf supernovae follow a period-luminosity relation, while massive supernovae do not.

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True

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Jets in radio galaxies and in protostars...

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