A White Dwarf (also called a Degenerate Dwarf) is a small star made of Electron-Degenerate Matter. On average, they have a mass similar to the Sun, but a size only comparable to the Earth. They are very dense, but only faintly luminous (at least, compared to other stars). They comprise roughly 6% of the stars detectable from Earth.
Past and Composition
White Dwarfs do not have their own internal fusion process - their glowing is the result of stored thermal energy from some previous state. Most White Dwarves were previously main sequence stars, that cooled down and shed their outer layer. The discarded layer becomes a planetary nebula.
- Carbon and Oxygen - the most common type of White Dwarf
- Oxygen, Neon, and Magnesium - less common, but a little hotter than the previous type. These can actually fuse carbon for a while.
- Helium - unlike other forms of White Dwarf, these Helium White Dwarf Stars are caused by mass loss, where the presence of some other star or giant planet in the system causes stellar matter to radiate away.
The White Dwarf wil eventually become some other form of Compact Star:
- After a long passage of time, most White Dwarfs will cool down and eventually become Black Dwarf Stars. However, it's believed no Black Dwarves exist yet, as the universe itself is not old enough for any stars to go through the whole process of yellow-dwarf to red-giant to white-dwarf to black-dwarf.
- If the White Dwarf instead accumulates mass, via collisions, or mass transfer from a companion star, it may explode as a Type IA Supernova (see also Supernova). To do so, it needs to only grow to about 1.4 times as massive as our Sun. After the explosion, the remaining material will collapse and become a neutron star, black hole, or other exotic.
Game and Story Use
- When the Yellow Dwarf star turned into Red Giant, it burned the life from the surface of the orbiting worlds. Then it collapsed into a white dwarf, and ejected matter back towards those planets. The new matter rekindled life on the planets. Or life remained far beneath the burning surface and survived with minimal light, just heat - and can now return to the surface lit only by a White Dwarf. Either way, you'd end up with extremophiles, or possibly higher forms of life evolved from them.
- Another variation on the concept - intelligent life evolved on the planet before the sun went Red Giant. They didn't have time to properly colonize any other planetary systems, so they buried genetic repositories deep within the planet, or set them in far orbit. Automated systems used the repositories to recolonize the planet long after the star had collapsed to a White Dwarf. Boom! Ecosystem and intelligent life orbiting a white dwarf.