gravitational waves emerge following the violent deaths of rapidly rotating stars 15 to 20 times the mass of the sun. Upon running out of fuel, these stars implode, then explode, in an event known as a collapsar. This leaves behind a black hole surrounded by a large disk of leftover material that quickly whirls into the black hole’s maw. The spiraling of material — which lasts just minutes — is so great that it distorts the space around it, creating gravitational waves that travel across the universe.