Black hole animation. A black hole is a region of spacetime with a gravitational field so strong that even light cannot escape it. It is thought that stellar mass black holes are created by the core collapse of a massive star when it runs out of fuel, and it is also thought that most if not all galaxies have a supermassive black hole at their centres. Black holes pull surrounding material towards them through their strong gravitational field. They can be detected by the accretion disc around them, within which infalling matter heats up, and emits radiation.