White Dwarf란 무엇인가?
A white dwarf is the exposed core left behind when a star like the Sun runs out of fuel and sheds its outer layers. It packs up to 1.4 solar masses into a sphere roughly the size of Earth, at densities around a tonne per cubic centimetre — and it has no fusion left. It is an ember.
Nothing is burning inside a white dwarf. What holds it up against its own gravity is electron degeneracy pressure, a purely quantum effect: the Pauli exclusion principle forbids electrons from occupying the same state, so they resist being squeezed even at absolute zero. This gives white dwarfs a bizarre property — the more massive one is, the smaller it gets.
That relationship has a hard ceiling. Above about 1.4 solar masses — the Chandrasekhar limit, derived by Subrahmanyan Chandrasekhar in 1930 — degeneracy pressure loses to gravity and the star cannot survive. A white dwarf pushed past that limit by stealing gas from a companion detonates as a Type Ia supernova, the standardised explosion that let astronomers measure the accelerating expansion of the universe.
Left alone, a white dwarf just cools. Starting above 100,000 K, it radiates away its residual heat over billions of years, dimming from blue-white to yellow to red. As the interior cools, the carbon and oxygen ions lock into a crystal lattice — a genuinely diamond-like solid core, confirmed by Gaia observations in 2019. Given enough time it becomes a cold, dark black dwarf, but the universe is not remotely old enough for one to exist yet.