astronomy 15 – Flashcards
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Compared to the spirals, elliptical galaxies tend to be more dusty.
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false
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Despite varying masses, all spiral galaxies look essentially the same.
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false
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Unlike spirals, elliptical galaxies do not contain a flattened disk.
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true
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Most galaxies are spirals.
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false
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Irregulars typically have very few blue stars.
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false
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On average, elliptical galaxies are richer star forming regions than spirals.
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false
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Irregular galaxies, although small, have large star-forming (HII) regions and much ongoing star formation for their size.
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true
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M31 in Andromeda is a bigger version of our Galaxy, and the largest member of the Local Group.
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true
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Virtually all galaxies are moving away from the Milky Way.
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true
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Quasars can emit thousands of times as much energy as normal galaxies.
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true
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Quasars are the brightest objects in the universe.
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true
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Active galaxies emit most of their radiation as visible light
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false
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On average, active galaxies are rare and most are fairly distant from us
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true
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The light output from some quasars varies in just a few hours.
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true
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There is evidence that a collision between a spiral and an elliptical galaxy has produced a radio galaxy.
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true
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Which property is common to spiral galaxies?
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NOT ongoing star formation and emission nebula in the halo
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Compared to our own Galaxy, elliptical galaxies
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show no evidence of ongoing star formation
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What is true of giant and dwarf elliptical galaxies?
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The giants contain more total mass than the dwarfs
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A galaxy with little cool gas or dust and no evidence of ongoing star formation is most likely a(n)
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elliptical
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Which of these would be made up of only Population II stars?
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elliptical galaxies
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Why does the Cepheid distance method fail us beyond about 20 Mpc?
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Even with the HST, the most luminous Cepheids are too faint to be seen beyond 20 Mpc
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What are Type I supernovae used for?
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Standard candles for determining distances to other galaxies
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Most of the galaxies in the Local Group are
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small ellipticals like the companions to M31 in Andromeda
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According to Hubble's Law, the greater a galaxy's redshift, the
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farther it is from us
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While examining the spectrum of a galaxy, you find all the hydrogen lines are shifted to longer wavelengths. This galaxy is
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moving away from us
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Why is the energy source for active nuclei like Seyferts thought to be compact?
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The light can vary over short time intervals
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Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiative energy.
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an accretion disk of infalling matter
