White-Dwarf Cooling Sequence

What you are seeing: a white dwarf of mass $M$ cooling under the Mestel law $L(t) \propto M t^{-7/5}$ . The HR diagram at the top traces the cooling track (blue point = current age); the WD sphere and cross-section on the bottom show the photosphere colour by $T_{\rm eff}$ and the inward-growing crystal core (yellow) once $\Gamma > 175$

Figure 1. White-dwarf cooling: HR-diagram track + interior crystallization front. Method: Mestel L ~ M t^(-7/5), Stefan-Boltzmann T_eff = (L / 4 pi R^2 sigma)^(1/4), Eggleton M-R relation.

mass M / M_sun0.60

log age (years)9.00

animation speed1

show LF bumpon

WHAT TO TRY

Scrub the age: the white dwarf fades down the Mestel cooling track L ~ M t^(-7/5), its temperature and luminosity falling as it radiates its stored heat with no fuel left.
Change the mass: a heavier white dwarf is smaller and cools differently, and the HR-diagram track shifts. Cooling age is a clock for the oldest stars in the galaxy.
Toggle the luminosity-function bump: crystallization of the carbon-oxygen core releases latent heat, pausing the cooling and piling up white dwarfs at that luminosity.