Re:UHZ1: NASA Telescopes Discover Record-Breaking Black Hole
by denton-scratch on Tuesday November 07, 2023 @08:09AM
(#38176317)
> So gas clouds contracting to form very massive black holes had to work against the expansion to do so.
Is that correct? My understanding is that the expansion of the Universe occurs away from large concentrations of mass; expansion doesn't cause the stars in a galaxy to move apart.
No, it doesn't. There are indeed upper limits on the mass of objects that are formed from stars that run out of nuclear fuel, before the objects collapse to black holes (the Chandrasekhar limit for white dwarfs and the Tolman-Oppenheimer-Volkoff limit for neutron stars), but those limits are not based on density.
It is true that, especially in the early universe, gas clouds forming very massive black holes without going through the intermediate stage of forming stars is considered possible; but that is not based on the kind of simplistic calculation that you describe. It's based on numerical simulations of the Einstein Field Equation with relevant initial conditions.
Another factor you are not considering is that the universe is expanding, and the early universe was expanding much more rapidly than our current universe is. So gas clouds contracting to form very massive black holes had to work against the expansion to do so. That further complicates the calculations.