[hparadiz]

Little red dots are my favorite new concept in astrophysics. This idea that there could be so much matter orbiting a black hole that the matter reaches sun levels of pressure which in turn starts steller fission without there being an star. Mind-blowing

[stouset]

Yep, it’s a super cool concept. A black hole of a given size has a finite amount of matter that it can ingest over a period of time. Trying to stuff more matter into it causes an outward pressure from essentially the friction of the swirling mass of material falling in. This radiation pressure could in theory be great enough to start fusion as would happen in a stellar core.

Also fun is that this puts a limit on the largest possible black hole we should ever see in the universe. If you assume a black hole formed a moment after matter condensed and then ingested the maximum possible from then until now, you get an upper bound for the largest possible black hole according to our current understanding of the universe. This limit is somewhere around 36 billion solar masses.

[technotony]

Couldn't those large black holes merge though to get bigger ones?

[muvlon]

Yes, exactly. Black hole mergers are the one thing exempt from the Eddington Limit, because there is no friction there.

[rolph]

a tokomok involving a scale appropriate blackhole is a super cool concept that just came to mind

[lenkite]

Will all matter in the universe just collapse into black-holes eventually ? It feels that way. And will all the black-holes then merge to form the Primordial Black Hole which will then explode to form a new universe ?

[Larrikin]

All of the evidence currently points the universe expanding and bringing everything further apart. There is no evidence of a cycle. However, some people are starting to believe the expansion is slowing.