Black holes are getting stranger — even to astronomers. They’ve now detected the signal from a long ago violent collision of two black holes that created a new one of a size that had never been seen before.

“It’s the biggest bang since the Big Bang observed by humanity,” said Caltech physicist Alan Weinstein, who was part of the discovery team.

Black holes are compact regions of space so densely packed that not even light can escape. Until now, astronomers only had observed them in two general sizes. There are “small” ones called stellar black holes that are formed when a star collapses and are about the size of small cities. And there are supermassive black holes that are millions, maybe billions, of times more massive than our sun and around which entire galaxies revolve.