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18 Cards in this Set
- Front
- Back
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period luminosity relation
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more massive stars pulsate more slowly than less massive stars
brighter stars=longer pds |
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based on gobular clusters..
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galactic center is in direction of sagitarius
sun is not at center of galaxy, but does lie on disk |
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galactic components
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1.disk=mostly stars, gas and dust. ongoing star formation
2.halo=spherical cloud of stars and gobular clusters. little gas and dust 3.nuclear bulge=dense, spherical cloud around center of galaxy. little gas and dust in outer region |
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population I stars
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found in disk of galaxy
higher percentage of metals circular orbits relatively younger stars |
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population II stars
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found in halo and bulge
lower percentage of metals elliptical and tilted orbits older stars |
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first stars
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mostly hydrogen and helium
low mass stars still around high mass stars evolved into supernova |
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halo and disk origin
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1spherical cloud of dust gives birth to star/star clusters
2.rotating cloud begins to contract, leaving stars behind in halo w/ random motions 3.new generations of stars have flater orbitations and more ordered motions 4.disk of galaxy now very thin |
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density wave theory
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orbiting gas clouds take spiral arms from behind.
compression of gas cloud triggers star formation massive OB stars light up but die quickly low mass stars live long but not luminous |
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age of galaxy
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open clusters (in disk)=7 billion years old
globular clusters (in halo)=11 billion years old disk younger than halo |
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sagitarius A
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high lumionsity->lots of dust and crowded w/ stars
spiral arms of material flowing from disk to Sgt A* |
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Elliptical galaxy
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egg-shaped
little gas or dust (no ongoing star formation) reddish/yellowish color (lack of hot OB stars) older stars |
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Spiral/Barred Spiral galaxy
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"disk" galaxy
disk and spiral arms lots of gas and dust (ongoing star formation) bluish/whitish (hot luminous OB stars) form new stars |
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Spiral galaxies classed based on...
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1. amount of gas and dust
(Sa= least, Sc=most) 2. size of nuclear bulge (Sa=largest, Sc=smallest) 3.tightness of spiral arms (Sa=tightest, Sc=loosest) |
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Irregular galaxy
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no clear pattern
gas, dust, stars |
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tully-fisher relation
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rotation speed of galaxy directly related to total luminosity
greater mass=faster a galaxy rotates greater mass=more light it gives off |
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local group
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30-40 galaxies, mostly dwarf ellipticals
dominated by milky way and m31 (andromeda) |
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galaxy supercluster
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dominated by Virgo cluster (2500 galaxies)
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hubbles law
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galaxies farther away-> moving away from us at faster and faster speeds
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