How much hydrogen could you amass before it would form a black hole?

If you could pile up plain hydrogen and have it overcome the solar wind generated, could you gather up enough that it would undergo gravitational collapse?


If you gathered up enough hydrogen, it would form a star and the energy from the nuclear fusion would keep it from collapsing further for a while. Once the fuel runs out (though a series of other reactions) it would collapse into black dwarf, neutron star, or black hole depending on how much is left.

If the remaining matter is 3 times the mass of our sun it will form a black hole. A quick search indicates that it would need to start the process with 25 solar masses to end up with 3 solar masses after burning for that long and the inevitable supernova near the end of the cycle.

It would undergo nuclear fusion long before nuclear degeneration.

Get more hydrogen, and it’ll still burn before it goes black; it’ll just burn quicker. Eventually, though, there is some quantity of hydrogen that would go black before it burned (but which would still burn at some point before reaching the singularity).

How much?

25 solar masses, and a whole lot of time.