lecture08 - Stars Galaxies and the Universe Marua Brada AST...

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Stars, Galaxies and the Universe Maru š a Brada č AST 10G: Stars, Galaxies and the Universe Lecture 8: What is our Universe made of? Our Galaxy
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Stars, Galaxies and the Universe Maru š a Brada č Today on AST 10G Our Milky Way
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Stars, Galaxies and the Universe Maru š a Brada č Movie by B. Tully
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Stars, Galaxies and the Universe Maru š a Brada č Movie by B. Tully
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Stars, Galaxies and the Universe Maru š a Brada č The Light Side of the Universe Our solar system - 1 star The Milky Way contains about 2 × 10 11 stars
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Stars, Galaxies and the Universe Maru š a Brada č Milky Way: What Is It? A river of stars? A pancake? Something else? Try counting stars and their apparent brightnesses in various directions. Herschels (1700's) and Kapteyn ( 1900): we are near the center of a pancake. Shapley (1910's): found distances of star clusters, came to very different conclusion!
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Stars, Galaxies and the Universe Maru š a Brada č Shapley's Map: Where Are We?
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Stars, Galaxies and the Universe Maru š a Brada č Why Was Kapteyn Wrong? Trumpler (1920's): star counts are deceptive because of dust! Now very well characterized with infrared and other means.
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Stars, Galaxies and the Universe Maru š a Brada č “Spiral Nebulae” known since 1700's with telescopes of the time, not clearly different from planetary nebulae and star-forming regions Kant (1755): “island universes” like the Milky Way? Shapley and Curtis debated this hypothesis in 1920...how would you judge it? M31
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Stars, Galaxies and the Universe Maru š a Brada č Argument in favor: This looks just like our model of the Milky Way, so the Milky Way is just one of many. Rebuttal: For something as large as the Milky Way to look this small, the universe would have to be unimaginably, ridiculously large M31
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Stars, Galaxies and the Universe Maru š a Brada č Shapley-Curtis Debate Argument opposed: a nova appeared in M31, which had a large apparent brightness, proving that M31 is not distant. Rebuttal: all other novae in M31 were much fainter than the one Shapley cites. Who you gonna believe, the one or the many? M31
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Stars, Galaxies and the Universe Maru š a Brada č Shapley-Curtis Debate Argument in favor: why does M31 have so many novae anyway? Possibly because it has billions of stars in it? Rebuttal: we don't know what causes novae, so that doesn't prove anything M31
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Stars, Galaxies and the Universe Maru š a Brada č Shapley-Curtis Debate Argument in favor: von Maanen detected M101 rotation in plane of sky. If it were big, it would have to be rotating faster than speed of light!
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