Stars and Galaxies

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have a disk but no arms

have little or no excess gas and dust

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Irregular Galaxies

any galaxy that isn’t a Spiral, Elliptical, or Lenticular

usually have lots of gas and dust and young stars

may have a distorted shape from interaction with another galaxy

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Irregular Galaxies

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Collisions!

We now think that galaxies in groups and clusters often collide

The Milky Way is moving at 300,000 mph toward the Andromeda Galaxy

They may collide in about 5 billion years

Stars don’t usually collide

New orbits, gas piles up to form new stars

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Interacting

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the Antennae or Mice

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The occasional results of two galaxies colliding: ringed galaxies

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Various galaxies (can you identify types?)

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Supermassive black holes

almost every medium to large galaxy we’ve check has a supermassive black hole at the center

the larger the galaxy, the more massive the black hole

we don’t know which comes first, the galaxy or the black hole

we think that these black holes are responsible for some of the galaxies with jets and lobes which give off radio waves, x-rays, etc.

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Active galaxy

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at the center of a large galaxy

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Galaxy Clusters

the Local Group

includes the Milky Way, the Andromeda, and over 30 other smaller galaxies

the Virgo Cluster

hundreds to thousands of galaxies, 60 million light-years away

giant elliptical at center, formed by galactic cannibalism

the Local Group is “falling” toward the Virgo Cluster at 60 to 250 miles per second!

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Coma Cluster

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Superclusters!

clusters are bound together in larger structures, called superclusters