White Dwarf
The hot, dense remnant of a star that has exhausted its fuel and shed its outer layers, leaving behind a compact core of electron-degenerate matter that no longer fuses.
A white dwarf is the hot, dense stellar remnant left behind after a star of roughly solar mass exhausts its hydrogen fuel, swells into a red giant, and sheds its outer layers. This object represents the standard endpoint for stars like our Sun and is composed of electron-degenerate matter that no longer undergoes fusion. It is extremely compact yet retains significant mass, eventually cooling over billions of years.
What this means in real life
When our Sun dies in about 5 billion years, it will shed its outer atmosphere and leave behind a white dwarf—a glowing ember the size of Earth but as heavy as the entire Sun, slowly cooling over trillions of years.
What it isn’t
Not a black hole or neutron star. White dwarfs are much less dense than neutron stars and form from lower-mass stars; they don't collapse into black holes because their mass is insufficient to overcome electron degeneracy pressure.
Commonly misused online
Often conflated with 'dead stars' generically, when actually only low- to medium-mass stars become white dwarfs; massive stars become neutron stars or black holes instead.