Recent comments in /f/science

afrothunder1987 t1_je5tkye wrote

For reference, Sagittarius A*, the supermassive black hole at the center of the Milky Way is 4.3 million times the mass of the sun.

https://beta.nsf.gov/news/astronomers-confront-massive-black-hole-heart

At 30 billion times the mass of the sun this thing is….. big

Ultra massive black holes like this present a problem for science. Accretion disks can only become so hot, dense, and energetic around black holes before they radiate so much energy that they keep themselves from falling into a black hole above a certain rate. There is effectively a limit to how fast black holes can grow.

These super/ultra massive black holes are bigger than it should be possible for them to be, even if they experienced max growth rate constantly from the birth of the universe.

So how did they get that big?

A cool theory is that when the universe was young, dense, and hot, enormous stars formed that were so massive their cores compressed into black holes. And because these black holes are surrounded by a star which is constantly crushing matter into it, the black holes basically get force fed. The accretion disk energy is overwhelmed by the crushing pressure from the gigantic Star.

It’s a fun theory.

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zoinkability t1_je5powt wrote

There is a direct relationship between the mass of a black hole and the size of its event horizon. if you know the one, you know the other. So if a black hole is the highest mass ever seen, it would also be the largest in terms of its event horizon.

That said, inside the event horizon we simply can't know what goes on. So the "actual size" (meaning, how much space the matter inside the black hole occupies) is, I believe, simply unknown.

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SpererZero t1_je5pjqj wrote

It's mass directly as effects it's size, remember, it's not the physical object that's big, but rather the schwarchchild radius, where light can no longer escape.

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DoyoureadmeHAL t1_je5hrt3 wrote

So it says “mass” of the sun but then they mention “something that large” implying size. I’m a dummy but those are two different things right. It could be the size of a baseball and be 30 billion times the mass of the sun. No?

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