When the small but dense white dwarf is formed from a star like the Sun, the core temperature is not high enough to permit the carbon and oxygen to participate in further energy-producing nuclear reactions. But why does this dense core not produce energy by the Kelvin-Helmholtz contraction?

Question

Quizplus · Accepted Answer

The core of the white dwarf is supported by electron degeneracy pressure, which resists further compression and contraction. This pressure arises from the fact that electrons, being fermions, cannot occupy the same quantum state and must fill higher energy states as the core compresses. As the number of electrons per unit volume increases, their average kinetic energy also increases, generating a pressure that holds up the core against further contraction. Therefore, the Kelvin-Helmholtz contraction cannot occur in a white dwarf.

When the Small but Dense White Dwarf Is Formed from a Star