Failed supernova

A failed supernova, also known as an unnova, is the opposite of a supernova. When a large enough star runs out of fuel, it turns into a red supergiant. When these stars die, they cause an incredible explosion. This is a supernova. In the case of a failed supernova, the star will just collapse into a black hole. It does not explode into a supernova.
Failed supernovas may be a cause of rogue planets. Rogue planets are planets without a star.