White Dwarfs

At the end of its life, a star the Sun’s size will expand into Red Giant. In its core it fuses helium nuclei together to make carbon and oxygen, but a star of this mass lacks the energy to fuse carbon any further than this so the fusion process stops. The red giant eventually pushes away its outer layers to form a planetary nebula, and leaves behind its core

The core of the dead star collapses under its own gravity into a tiny remnant - a White Dwarf. These stars are only a few thousand kilometres in radius, a similar size to Earth, and are about 1000000 times denser than the Sun - between 107 and 1011 kg per cubic meter

These stellar remnants are known to accrete matter since they have exceptionally strong gravitational pulls - almost the entire mass of the Sun condensed into a ball the size of Earth would have very strong gravity - devouring whatever gets too close. Some of these stars are in binary systems with much larger stars, just like Sirius A and B pictured above, where the white dwarf may suck matter straight off the other star! If the white dwarf absorbs enough mass it can collapse into a Neutron Star, and eventually a Black Hole

The Sun will become a white dwarf in about 6000000000 years after burning Earth to ashes in its red giant phase. Pleasant thought

Image Credits: Nasa, ESA