Galaxies and the Universe

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Galaxies and the Universe

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What Are Galaxies?

Greek galax = milk

William Herschel, 1783: A disk with the Sun slightly off-center

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What Are Galaxies?

19th Century: “Spiral Nebulae”

Nearby? Maybe Solar Systems in Formation?

1920: Galaxies are Stars

1920’s: Galaxies are like the Milky Way

Biggest single increase in our mental picture of the Universe in human history

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Where Are We in our Galaxy?

The visible Milky Way suggests our galaxy is a flat disk

Surrounding other galaxies is a spherical halo of Globular Star Clusters

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Galaxies and Globular Clusters

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The Milky Way’s Globular Clusters

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The Milky Way As We See It

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Anatomy of a Galaxy

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Spiral Arms

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In Microwaves, We Can See the Hub of the Galaxy

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Mapping the Neighborhood

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Mapping the Neighborhood

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Mapping the Galaxy: Not There Yet

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Mapping the Galaxy: Not There Yet

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The Local Group

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Downtown: The Virgo Cluster: 50 m.l.y

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The Local Super-cluster

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The Coma Cluster 350 m.l.y.

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