Accretion

Narration: Katy Mersmann

Transcript:

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Accretion. In short, accretion

means growth by accumulation.

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Land on Earth can form from accretion

of soil deposited by rivers or sea.

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Planetary bodies can also grow

from accretion as gravitational forces

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attract debris and other matter.

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But we want to talk about

accretion in astronomy.

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Accretion is one way

we can see black holes.

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Black holes have intense

gravitational mass,

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pulling in everything in the vicinity,

including light.

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Without that light,

we can't see black holes, but we can see

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the disk-shaped flow of gas and dust

that forms around some black holes.

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We call these accretion disks,

and they can form around

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black holes of any size,

as well as around some stars.

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Material in black hole accretion disks

is really hot, like millions of degrees.

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This is caused by the collision

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of particles in the accretion disk

as they are pulled into their black hole.

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These collisions can cause

accretion disks to release X-rays,

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which can allow us

to locate some black holes.