The lives of black holes, from birth to death

Of all the strange and spectacular things in outer space, nothing is stranger or more spectacular than black holes.

These cosmic oddballs can’t even be described without contradiction. Unlike a typical hole, for instance, a black hole is not empty. Its core packs so much matter that its density is almost impossible to imagine. The smallest known black holes squeeze more than three times the mass of the sun into a volume about the diameter of a small city. One of the largest that scientists have found contains more than tens of billions of times the mass of the sun and stretches across a space bigger than the solar system.

Because it holds so much mass in such a small space, nothing that gets too close to a black hole can escape its gravity — not even light. Yet to find black holes, scientists must look for the brightest beacons of light in space. (This light is given off as the black hole feeds on nearby gas.)

Explainer: What are black holes?

Black holes have been...