A very high-mass star fuses hydrogen into helium quickly and furiously. Having one hundred times the mass of the Sun, these stars have a main sequence lifetime of about one million years and a luminosity a million times that of the Sun. Like a high-mass star, a very high-mass star leaves the main sequence and fuses heavier and heavier elements. When—or if—a supernova explosion occurs, however, the core does not stop collapsing at a neutron star. Rather, the mass of its core is so great—up to ten or twenty solar masses—that no kind of ordinary matter can arrest the gravitational infall. The mass piles into a singularity and becomes a black hole.