Black holes are compact regions of space so densely packed that not even light can escape. There are "small" ones called stellar black holes that are formed when a star collapses and are about the size of small cities. Then in May 2019 two detectors picked up a signal that turned out to be the energy from two stellar black holes — each large for a stellar black hole — crashing into each other. Black hole collisions have been observed before, but the black holes involved were smaller to begin with and even after the merger didn't grow beyond the size of typical stellar black holes. It could instead be that supermassive black holes were formed in the immediate aftermath of the Big Bang.

Source: Daily Sun September 02, 2020 12:11 UTC