When did it take place, and what was the cause of the first back hole in the universe? Does this time precede stars collapsing as a result of old age?

  • $\begingroup$ First we need to find it... $\endgroup$ – user24157 Mar 1 '20 at 11:50
  • $\begingroup$ Is it possible to somehow go back and time to find it or do the equations of physics shed insight? $\endgroup$ – user31880 Mar 1 '20 at 11:51
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    $\begingroup$ Nobody knows. See en.wikipedia.org/wiki/Primordial_black_hole BTW, stellar black holes form from large stars, and large stars have short life spans, so they're much younger than the Sun's present age when they collapse. A 20 solar mass star (about the smallest that can produce a black hole) lives for about 10 million years. It's possible that a slightly less massive star can end up as a BH via a failed supernova, but the lifespan of such stars isn't thst much longer. $\endgroup$ – PM 2Ring Mar 1 '20 at 12:21
  • $\begingroup$ Black hole or back hole? Important difference. $\endgroup$ – Michael Harvey Mar 2 '20 at 19:40

We don't know for sure.

It is possible that random fluctuations in the density of matter of the early universe created black holes that could be much smaller than regular black holes formed by stellar collapse. These would have formed in the moments after the big bang.

Otherwise the first stars formed about 400 million years after the big bang, and some of these could form black holes after their (short) lives. Stars over 250 solar masses (which could form in the early universe) would produce large black holes when they collapsed.

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    $\begingroup$ en.wikipedia.org/wiki/Primordial_black_hole might be an interesting reading about those early black holes. $\endgroup$ – Pere Mar 1 '20 at 19:40
  • $\begingroup$ I think the terminology describing the black holes as tending to "fall towards the centre of galaxies" is problematic. Do you mean migrate to the center of galaxies? Do you have any sources to cite for this statement? $\endgroup$ – Bob516 Mar 1 '20 at 20:08
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    $\begingroup$ dynamical friction: gravitational interactions will tend to transfer energy and momenum from massive to smaller bodies. But this is hardly a key part of the answer and I'll delete it. $\endgroup$ – James K Mar 1 '20 at 20:42

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