WEBVTT

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[MUSIC PLAYING]

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Are all galaxies the same?

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We live on a planet in
a single solar system,

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inside a large galaxy made up
of a hundred billion stars.

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A supermassive black hole equal
to the weight of a few million

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suns anchors the
center of our galaxy.

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Our universe has
hundreds of billions

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of galaxies, each containing
stars like our sun.

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Galaxies range in size
from ones with 1,000 stars

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to ones with a
trillion or more stars.

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That means we have a lot
of places to explore.

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Edwin Hubble was one of
the first astronomers

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to discover that our universe
isn't just sitting still,

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but it's expanding.

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Hubble also grouped
galaxies by how

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they looked because not
all galaxies are the same.

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He described a few
distinct types.

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Elliptical galaxies, which
have no easily defined

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shape with stars that
move chaotically.

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And spirals or disk
galaxies, which

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are flat with pinwheel
spiral arms that

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spread out from the center.

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As Hubble began to
classify galaxies,

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he quickly discovered many
galaxies didn't fit neatly

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into his categories.

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Was it possible that
galaxies change from one type

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to another over eons?

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Even our own Milky Way
galaxy has been changing.

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There are a handful
of smaller galaxies,

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such as the Magellanic
clouds, Fornax, Sculptor, Leo

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and others that orbit around us.

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The powerful gravity
of the Milky Way

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affects these nearby
galaxies, either causing

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them to be ripped
apart, or pulling them

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into merge with ours.

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[MUSIC PLAYING]

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