Nothing in the universe is more violent than the collision of two black holes. At that instant, the impact releases more energy than every star in the universe combined. It also creates ripples in spacetime that
travel at the speed of light, known as gravitational waves. Though invisible, they appear as blue lines in this image created by a NASA supercomputer.
Here we watch as two spiral galaxies collide and create a third galaxy with a huge black hole at its center. The hole grows and grows until, with its enormous energy, it heats surrounding gases and hurls them out into the universe. The result [right] is an elliptical galaxy with very little gas and not much star creation. Researchers at the Max Planck Institute for Astrophysics illustrated this simulation using red to show the hottest gases and blue for the coldest. The brighter the color, the denser the gas.