Eternal Flames: Unraveling the Mystery of Delayed White Dwarfs

Researchers discovered why some white dwarfs remain luminous for billions of years: a core process where lighter crystals rise and denser liquids sink, balancing the energy and maintaining surface brightness.
Your astronomy textbook might describe white dwarfs as the cool and comparatively uninteresting remnants of dead stars. This perspective is challenged by the previously unexplained existence of delayed white dwarfs, which defy expectations by shining as brightly as some familiar main-sequence stars for billions of years.

New research by Simon Blouin with co-authors at the University of Warwick and the Institute for Advanced Study, in Princeton, NJ reveals that in the cores of these strangely behaving stars, lower-density crystals form and float up while denser liquids with heavy impurities sink. This process of solid-liquid distillation interrupts cooling for billions of years and explains all the observed properties of the unusual population of delayed white dwarfs.