# Black hole size

what is the smallest possible size of a black hole?

I'm taking it you mean the centre-singularity? I heard it could be as small as an atom, or something called planck length...

Wondered this myself as well.

phyzguy
A black hole the mass of the sun is about 3 km in radius (Schwarzschild radius or radius of the event horizon), and the radius is directly proportional to the mass. If you can compress matter to a high enough density you can theoretically make a black hole arbitrarily small, but practically there is no known way to create black holes except in the collapse of massive stars. The smallest black hole that we know of is about 5 solar masses, so about 15 km in radius. There is a hypothesis that smaller black holes could have been created during the very early phase of the big bang, but these have never been seen.

A black hole the mass of the sun is about 3 km in radius (Schwarzschild radius or radius of the event horizon), and the radius is directly proportional to the mass. If you can compress matter to a high enough density you can theoretically make a black hole arbitrarily small, but practically there is no known way to create black holes except in the collapse of massive stars. The smallest black hole that we know of is about 5 solar masses, so about 15 km in radius. There is a hypothesis that smaller black holes could have been created during the very early phase of the big bang, but these have never been seen.

I have wondered in the past if there would have been black holes from the early phase of the big bang, it definitely seems possible.

One question. Is it true that the larger stars with more mass will become smaller black holes as they will collapse further under their own pressure? Or does it not work like that? I don't know much about physics so excuse any questions that might be stupid haha

phyzguy
One question. Is it true that the larger stars with more mass will become smaller black holes as they will collapse further under their own pressure? Or does it not work like that? I don't know much about physics so excuse any questions that might be stupid haha

No. The Schwarzschild radius of a black hole is directly proportional to the mass, so the larger the mass, the larger the black hole.

No. The Schwarzschild radius of a black hole is directly proportional to the mass, so the larger the mass, the larger the black hole.

Thank you for clearing that up

will the 15 km black hole also have 'event horizon'?

George Jones
Staff Emeritus
Gold Member
will the 15 km black hole also have 'event horizon'?

Yes. If it didn't, it wouldn't be a black hole.

are we having proof for the existance of event horizon ? or can we explain a blackhole with out the concept of event horizon?

Chronos