Carbon-Oxygen Phase Separation in a Crystallizing White Dwarf

This simulation renders a small cell of a white dwarf's carbon-oxygen core as it crystallizes. Because the Coulomb coupling parameter Γ scales as Z^5/3, the higher-charge oxygen ions freeze into the lattice before carbon does at the same temperature. With phase separation switched on, that preference is modeled explicitly: the rising crystallization front captures oxygen ions first, leaving a carbon-enriched liquid buoyant above it — the denser oxygen-rich solid sinking under gravity releases extra energy on top of ordinary latent heat, which is the physical mechanism proposed to explain the pile-up of white dwarfs Gaia observes at intermediate luminosities. Drag the core-temperature slider down (or let Auto-cool do it) and watch the front rise, the readouts track live.