There's a gap in physics when it comes to explaining how Super Massive Black Holes (SMBH) were formed.
In short, for black holes up to about 100 times the mass of the sun, we can understand with currently known physics the mechanisms by which those are formed.
However anything more massive than that, we just can't explain. The universe simply isn't old enough for them to have formed by the merging of smaller black holes.
The larger a black hole is, the further out its reach extends. The larger the black holes, the further apart they are when they start to orbit each other. The further apart they are, the less energy is dissipated by gravitational waves as the black holes spiral toward each other. The universe isn't old enough for those low energy gravity waves to have brought 2 black holes of masses larger than ~50 solar masses together.
There are other mechanisms by which black holes approach each other. One of them is by consuming each other's accretion disks. I.e. the black holes are basically experiencing friction as they move through each other's "atmosphere." (I'm using the word atmosphere purely metaphorically, here.)
Those other mechanisms don't have anywhere near enough energy in them to slow the black holes enough to make a difference at the mass scales I'm talking about.
These 1 million solar mass SMBH's seem to exist at the center of every galaxy.
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So that's a long-known issue with the Standard Model.
New research has proposed that dark matter can interact with other dark matter and annihilate, releasing energy in the form of photons. We do not observe this annihilation today because that interaction is so improbable and the universe has expanded and spread out the dark matter so much that it doesn't have the density needed for this self-annihilation anymore.
But in the early universe, when it was hotter and denser, if the above hypothesis is true, then we'd have so-called dark stars. The gravitational center of the dark matter could attract a million solar masses of Hydrogen into a huge cloud. The annihilation photons racing out from the center would provide the equilibrium pressure to prevent the Hydrogen from forming a core dense enough to begin fusion.
These dark stars would be enormous, bloated objects.
Eventually, the universe expands and cools and the dark matter interactions are lessened and start to run out. Then you have a million solar masses of matter no longer supported from gravitational collapse.
Et viola. SMBH's with 1 million solar masses collapse without ever really being a star powered by fusion.
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Data from the James Webb Space Telescope has produced 3 candidates for objects that might look like dark stars. They have the brightness, and seem to be point sources (as opposed to some cluster of other bright objects) and they exist long enough back in time.
This isn't confirmed physics, yet, but it's exciting that one of the big issues with understanding black holes and also dark matter may be culminating with some data to show an answer.
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