Stellar-sized black holes form when a star explodes in a supernova, leaving behind enough material that collapses to a distance within the black hole’s schwarzschild radius. as the core of the star collapses, its gravity becomes so strong that nothing—not even light—can escape from it. sort the following stars according to whether they could or could not collapse into black holes. could collapse into a black hole: could not collapse into a black hole: - the sun (1 solar mass) - eta carinae (100 solar masses) - spica a (11 solar masses) - betelgeuse (18 solar masses) - xi persei (40 solar masses) - sirius a (2 solar masses)