Black Holes Are Hard to Find

Black holes are hard to find. They have such strong gravity that light can’t escape them, so scientists must rely on clues from their surroundings to find them. When a star weighing more than 20 times the Sun runs out of fuel, it collapses into a black hole. Scientists estimate that there are tens of millions of these black holes dotted around the Milky Way, but so far we’ve only identified a few dozen. This image from 2001 is an artist's impression of a black hole accretion disk. Around many black holes is an accretion disk of material emitting energy as it falls into the black hole. Image Credit: XMM-Newton, ESA, NASA