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30 Cards in this Set
- Front
- Back
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Approx. how many stars does the milky way contain?
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Over 100 billion.
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What are Cepheid variable stars?
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Stars that change their brightness because they pulsate. They pulsate on periods of 1 to 60 days.
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What is the instability strip?
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The group of cepheid variable stars.
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What are proper motions?
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The movement of stars through space.
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What was the Shapley-Curtis debate?
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Curtis argued that there were other galaxies, Shapley said they were nebula in our galaxies.
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What is the disk component?
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All matter confined to the plane of the galaxy's rotation---everything in the disk itself.
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What is the diameter of the Milky Way?
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80,000 ly
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What are the spiral arms?
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Long curves of bright stars, star clusters, gas, and dust.
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What is the spherical component?
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All matter scattered in a spherical shape around the center of the galaxy.
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What is the halo?
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A spherical cloud of thinly scattered stars around the galaxy. No new stars form here.
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What is the Nuclear Bulge?
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Dense cloud of stars around center of galaxy. Due to no gas little star formation.
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What is the rough mass of the galaxy?
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100 billion solar masses
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What is a rotation curve?
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A graph of the orbital velocity of stars at various orbital radii in the galaxy.
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What is dark matter?
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An unknown form of matter held responsible for the the gravitational pull of galaxies.
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How old is our galaxy?
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roughly 9 billion years.
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What are population 1 stars?
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Stars that are the closest, brightest, and most easily studied. Located in the disk. Rich in metals
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What are population 2 stars?
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Stars that are dim, found in halo, clusters, and bulge. metal poor
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What does metals mean, in an astronomical sense?
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Atoms heavier than helium.
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What lies at the center of the galaxy?
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Hypothetically, a super massive black hole.
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What are spiral tracers?
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Objects used to map spiral arms.
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What is the density wave theory?
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Theory that spiral arms are waves of compression, that move around center triggering star formation.
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What does flocculent mean?
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Galaxies that have many short spiral segments, giving them a fluffy appearance.
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What is self-sustaining star formation?
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The process that causes "fluccolent" galaxies.
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What are radio galaxies?
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Galaxies that are bright at radio wavelengths.
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What are active galactic nuclei?
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Galaxies that have active nuclei, where there energy is emitted from.
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What are Seyfert galaxies?
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Galaxies with highly luminous nuclei and peculiar spectra.
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What are type 1 seyfert galaxies?
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Galaxies that are very luminous at X-ray and ultraviolet wavelengths and have the typical broad emission lines with sharp, narrow cores.
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What are type 2 Seyfert galaxies?
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Weak X-ray emission, narrower lines, but broader than normal galxies
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What are double-lobed radio galaxies?
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Galaxies that produce their energy from two radio lobes.
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What are Quasars?
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Small, powerful source of energy believed to be the active core of a very distant galaxy.
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