File:Gravitational lensing by black hole.tif

English: This illustration reveals how the gravity of a black hole warps space and bends the light of a distant star behind it. A black hole is the crushed remnant of a massive star that exploded as a supernova. The black hole traps light due to its intense gravitational field, hence it cannot be seen directly. The black hole distorts the space around it, which warps images of stars lined up almost directly behind it. This offers telltale evidence for the existence of lone black holes wandering our galaxy. The light from a background star is deflected and brightened by the black hole's intense gravitational field. The Hubble Space Telescope goes hunting for these black holes by looking for distortion in starlight as the black hole drifts in front of background stars.