White dwarf star. Artwork of an accretion disc (blue/white) around a white dwarf star (pale blue). A white dwarf is the final stage in the evolution of most stars. A star with a mass less than 1.4 times that of our Sun is thought to form a white dwarf. After it has used all its nuclear fuel, its outer layers escape into space, leaving the dense core behind as a white dwarf. It has the mass of a star compressed into the size of a planet. The strong gravitational field this causes attracts matter from surrounding space, which forms an accretion disc around the rotating star. The disc is heated by friction where it meets the star, causing it to glow brightly.