There are 10 billion white dwarfs in the Milky Way galaxy because many sunlike stars have already gone through the process of dying. Seven billion years later, the core of the sun will shrink to its remnant, a white dwarf, carrying about half of the solar mass with the rest lost.Ī white dwarf is a hot, dense, metallic crystal ball, roughly the size of the Earth-1.4 Earth radii in the case of WD 1856+534-that is slowly cooling off because it no longer has a central nuclear engine. In order to survive, our civilization will have to migrate outwards in the solar system.
In about a billion years, the sun will brighten up enough to boil away the oceans on Earth through a runaway greenhouse effect. Most likely, there are rocky, Earth-size planets at similar distances from other white dwarfs-in which case they would possess a surface temperature similar to that of Earth. Remarkably, this giant planet, WD 1856b, is seven times bigger than the stellar remnant it transits. Recently, the first planet to orbit a white dwarf-the latter named WD 1856+534-was discovered through its transit in front of the tiny star once every 1.4 days.