White Dwarf

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 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 can accrete matter from a companion star in a binary system, triggering a Type Ia supernova that completely destroys it.

The white dwarf is a transitional object in 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 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.