What is a white dwarf made of and how does it support its own weight? Does its temperature make any difference? What will eventually happen to a white dwarf?

1 Answer
Feb 4, 2017

This is one of my favorite things in Astronomy.


A white dwarf is made of degenerate matter, which is atoms, but the space squished between them. Its light comes from energy stored in it from its main sequence days. How does it hold its own weight? By one of my favorite principles in Astronomy (which reminds me of someone who is also my favorite ;-) the Pauli Exclusion Principle.

The Pauli Exclusion principle states that no two fermions (particles with half integer spins; in this case Electrons) can occupy the same quantum while in the same state. In white dwarfs, this is known as Electron Degeneracy pressure. Since they can't be in the same quantum (in the same state), they fly away from each other, counteracting the force of gravity.

Electron Degeneracy pressure does have a limit though, and this is the Chandrasekhar limit (saying this makes me think of that person ;-) fbp) which is 1.39 Solar Masses. If a white dwarf reaches this limit, it will explode in a type 1a Supernova. White Dwarfs usually accrete the needed mass to go SN by accreting mass from a binary partner.

If a white dwarf does not ever reach the Chandrasekhar limit, it will slowly lose it's stored energy to become a black dwarf. No black dwarfs are thought to have evolved yet because the universe is to young to have them.

I don't think that the temperature of a white dwarf matters.

This was for you fbp.