Stellar-mass black hole

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The third possible ending, reached when the collapsing core exceeds what neutron degeneracy and nuclear repulsion can support and no known pressure can halt the collapse. Unlike a white dwarf or a neutron star it is not a body with a surface but a region of spacetime from which nothing escapes, characterised by mass and spin alone. The progenitor mass range that produces one is poorly constrained: it depends on how much mass the star loses to winds before collapse, which depends strongly on metallicity, and on whether the explosion succeeds at all. Some massive stars are expected to collapse quietly with no bright supernova, and searches for such failed explosions have so far found them to be faint or rare. This is the one ending of the three whose formation has never been directly witnessed. Not a place on Earth.