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A '''white dwarf''' is the dense, Earth-sized remnant of a low- to medium-mass star that has exhausted its nuclear fuel and shed its outer layers. It is supported against gravitational collapse not by thermal pressure or nuclear fusion, but by [[Quantum Mechanics|electron degeneracy pressure]] — the quantum mechanical resistance of electrons to being compressed into the same quantum states. A white dwarf with a mass near the [[Chandrasekhar Limit|Chandrasekhar limit]] can accrete matter from a companion star in a binary system, triggering a [[Supernova|Type Ia supernova]] that completely destroys it.

The white dwarf is a transitional object in [[Stellar Evolution|stellar evolution]] — the endpoint for most stars in the universe, including the Sun. It is a degenerate stellar remnant that cools over billions of years, eventually becoming a cold black dwarf. The physics of white dwarfs connects [[Quantum Mechanics|quantum mechanics]] to astrophysics in a direct and testable way.

''The white dwarf is often treated as a stellar corpse, but this is incorrect. It is an active thermodynamic system — a cooling engine that continues to radiate for billions of years. The boundary between "living" and "dead" stars is not a biological one but a thermodynamic one, and the white dwarf is very much alive in the sense that matters for physics.''

[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Systems]]