2 upvotes, 3 direct replies (showing 3)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
How could small black holes exist if the large ones need huge masses the size of stars to be created
Comment by norasguide2thegalaxy at 20/07/2022 at 17:11 UTC
6 upvotes, 1 direct replies
Small black holes might have been formed directly by collapsing from small fluctuations in density in the early universe. These are called primordial black holes.
Currently, primordial black holes are predicted theoretically but have but been observed.
Comment by shitivseen at 20/07/2022 at 17:13 UTC
2 upvotes, 0 direct replies
I belive "small" is a very relative term. There are huge black holes that have swallowed many stars, and there are "small" black holes that were created by a single supernova. Also its not so much about the mass and more so about the density. A lot of mass is just a reliable way for gravity to create such densities. Finally, and this is still not proven, there might be a phenomenon called "hawking radiation" by which black holes would lose mass and "shrink".
Comment by kftrendy at 20/07/2022 at 17:21 UTC
2 upvotes, 0 direct replies
How small are you talking? Stellar-mass black holes (the smallest BHs that we observe) are formed when massive stars go supernova. We haven't observed any BHs smaller than a few solar masses. For stellar-mass black holes formed by the collapse of large stars, the original stars would be more massive than the BH, but not extremely so - a 20 solar mass star will produce a black hole with a mass of about 5 solar masses. We know that big stars like that exist - we see them all the time.
Theoretically, very low-mass black holes *could* form in the very early Universe (as in, before stars formed!) just by sheer chance - if a region of the Universe happened to get dense enough, it could collapse into a black hole. Unlikely, but possible.