The Cooling of White Dwarfs
A white dwarf shines not by nuclear reactions (unless it
is in a nova phase), but by radiating thermal energy.
Schematics of White Dwarf Cooling
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Remember Stefan-Boltzmann: L ~ R2T4.
So a hot white dwarf has a high luminosity...
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...but Luminosity represents an energy loss rate: L=dE/dT...
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and the energy of the white dwarf is thermal: E ~ NkT
So in the beginning, the WD is hot -- it radiates lots of
energy (its relatively bright) and cools rapidly. As it cools, it radiates
energy more slowly, and is less luminous. The evolution would look something
like this:
But they don't cool like this forever. As they cool, the
nuclei in the WD lose their thermal motions and settle into an ordered
crystalline lattice. This process releases heat, slowing the
cooling for a while. But eventually lattice vibrations cool the WD even
faster.
Ultimate end state: A crystallized
sphere of cold dark carbon/oxygen.
Question: What's another name for crystallized
carbon?