= Solution
The endpoint is set chiefly by the final core mass and composition, with envelope loss and binary interaction modifying the relation to initial mass. A star that never sustains hydrogen fusion is a <brown dwarf>, which cools; it is not a post-main-sequence remnant of a hydrogen-burning star. Very low-mass hydrogen-burning stars have such long lifetimes that their predicted eventual helium-white-dwarf endpoints need not yet be represented by isolated evolved examples.
Low- and intermediate-mass stars generally lose their giant envelopes and leave <white dwarfs> supported by <electron degeneracy pressure>. Most have carbon-oxygen cores; more massive degenerate cores may be oxygen-neon, while a <helium white dwarf> commonly results from binary stripping before helium ignition. The exposed hot core can ionize the expelled gas as a <planetary nebula>. The remnant subsequently cools without sustained central fusion. The <Chandrasekhar limit> constrains a cold nonrotating electron-supported core; it is not a universal initial-star mass cutoff.
More massive stars can proceed through advanced burning to an iron-group core. Further fusion of such nuclei does not provide energy, while electron captures and photodisintegration reduce pressure support and drain energy. Collapse can produce a <core-collapse supernova> and a <neutron star>, or a <black hole> if a sufficiently massive core collapses directly or gains substantial fallback. The remnant outcome depends on final core structure and the success of ejecting the mantle, rather than only on the original mass. Some oxygen-neon cores instead undergo an <electron-capture supernova>.
Binary evolution introduces additional branches: an accreting white dwarf may undergo <classical novae>, a thermonuclear <Type Ia supernova> leaving no ordinary white-dwarf remnant, or collapse in an appropriate core-composition regime. Extremely massive pair-unstable cores can be disrupted entirely by a <pair-instability supernova>. These possibilities are distinct from simple isolated-star cooling or ordinary core collapse. The broad white-dwarf/neutron-star/black-hole distinction follows the remnant support mechanism and surviving core mass; https://science.nasa.gov/universe/stars/[NASA's stellar overview] and https://science.nasa.gov/universe/stars/types/[stellar-type account] describe the corresponding observational classes.
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