A place with extreme gravity that not even light can escape. It has a infinitely dense center known as a singularity. Stellar mass black holes form when really big stars go supernova and have a few times Sols mass. Supermassive black holes are billions of times more massive than that. Black mini-holes have about the mass of a mountain. Black holes slowly evaporate through Hawking radiation when pairs of quantum-mechanically intertwined particles form due to the distorsion of spacetime just outside the event horizon, one of which escapes when the other enters the black hole.