Most black holes form from the remnants of a large star that dies in a supernova explosion. (Smaller stars become dense neutron stars, which are not massive enough to trap light.) ... When the surface reaches the event horizon, time stands still, and the star can collapse no more - it is a frozen collapsing object.

What causes the formation of black holes?

How Do Black Holes Form? ... Stellar black holes form when the center of a very massive star collapses in upon itself. This collapse also causes a supernova, or an exploding star, that blasts part of the star into space. Scientists think supermassive black holes formed at the same time as the galaxy they are in.

What is the purpose of black holes?

Supermassive black holes, in particular, might play an important role in star formation within galaxies, dictating when production slows or ceases altogether.