This gallery gathers together visualizations and narrated videos about black holes. A black hole is a celestial object whose gravity is so intense that even light cannot escape it. Astronomers observe two main types of black holes. Stellar-mass black holes contain three to dozens of times the mass of our Sun. They form when the cores of very massive stars run out of fuel and collapse under their own weight, compressing large amounts of matter into a tiny space. Supermassive black holes, with masses up to billions of times the Sun’s, can be found at the centers of most big galaxies. Although a black hole does not emit light, matter falling toward it collects in a hot, glowing accretion disk that astronomers can detect.