A white dwarf is a compact object resulting from the evolution of stars with initial mass <8 M⊙. It is essentially the stellar core, composed mainly of carbon and oxygen (or of helium for the less massive stars), which is uncovered after the planetary nebula phase. A typical white dwarf has dimensions comparable to the Earth’s and a mass comparable to the Sun’s, for a mean density of 106 g cm−3. Its internal pressure, due to the degenerate electron gas, can resist its gravity for as long as its mass remains below ∼1.44 M⊙ (the Chandrasekhar limit). White dwarfs emit thousands of times less electromagnetic radiation than the Sun, and they ultimately cool to black dwarfs. In binary systems, they may explode as novae or thermonuclear supernovae (SNIa).