Evidence for crystallisation in white dwarfs

Astronomers discover first direct evidence of white dwarf stars solidifying into crystals

The first direct evidence of white dwarf stars solidifying into crystals has been discovered by astronomers at the University of Warwick, and our skies are filled with them. Observations have revealed that dead remnants of stars like our Sun, called white dwarfs, have a core of solid oxygen and carbon due to a phase transition during their lifecycle similar to water turning into ice but at much higher temperatures.

https://phys.org/news/2019-01-astronomers-evidence-white-dwarf-stars.html