Core crystallization and pile-up in the cooling sequence of evolving white dwarfs

Understand

White dwarfs are stellar embers depleted of nuclear energy sources that cool over billions of years.

• These stars, which are supported by electron degeneracy pressure, reach densities of 1e7 grams per cubic centimetre in their cores.
• It has been predicted that a first-order phase transition occurs during white-dwarf cooling, leading to the crystallization of the non-degenerate carbon and oxygen ions in the core, which releases a considerable amount of latent heat and delays the cooling process by about one billion years.
• However, no direct observational evidence of this effect has been reported so far.