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Question
The distance to a star with a parallax angle of 0.2 arc seconds is ________.Answer
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Related questions
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Describe the reasoning leading to the idea that the number of technological civilizations in the galaxy is equal to the average lifetime of a technological civilization.
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A galaxy with a blueshift is moving ________ Earth.
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Our own Milky Way's Hubble class, according to the best data, is ________.
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The spiral arms are blue from the presence of Population ________ stars in them.
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When mass is accreted into a black hole, what fraction of the total mass-energy can be radiated away?
A) 0.007%
B) 0.08%
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Why is the energy source for active nuclei like Seyferts thought to be compact?
A) The sources appear to be single stars in photos.
B) Their energy appears to be non-stellar synchrotron radiation.
C) The light can vary over short time intervals.
D) We know the masses of the black holes that lurk there, and can find their radii.
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In active galaxies, their central engines may be temporarily fed by
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Describe the cycle of life and death we observe in the spiral arms.
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Compare the way an optical and radio astronomer would map the Galaxy.
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Why aren't there young stars in the halo?
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What advantage do radio astronomers have over optical ones in mapping the entire Milky Way?
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How did Herschel try to map our Galaxy 200 years ago, and why did he fail?
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Counting only the material between us and the galactic Center, we measure a mass of ________ billion Suns.
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The ________ is the spherical outer portion of the Galaxy, including the orbits of the globular clusters and most dark matter.
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Virtually the entire disk of the Galaxy has been mapped using the ________ wavelength.