https://en.wikipedia.org/wiki/White_dwarf
A white dwarf is the stellar core left behind after a dying star has exhausted its nuclear fuel and expelled its outer layers to form a planetary nebula.
白矮星（White Dwarf，也称为简并矮星）是一种低光度、高密度、高温度的恒星。 因为它的颜色呈白色、体积比较矮小，因此被命名为白矮星。 白矮星是演化到末期的恒星，主要由碳构成，外部覆盖一层氢气与氦气。
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to Earth's. A white dwarf's low luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf.[1] The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun.[2] The unusual faintness of white dwarfs was first recognized in 1910.[3]: 1 The name white dwarfwas coined by Willem Luyten in 1922.
