$^{22}$Ne Phase Separation As A Solution To The Ultramassive White Dwarf Cooling Anomaly

Understand

The precise astrometric measurements of the Gaia Data Release 2 have opened the door to detailed tests of the predictions of white dwarf cooling models.

• Significant discrepancies between theory and observations have been identified, the most striking affecting ultramassive white dwarfs.
• Cheng et al.
• (2019) found that a small fraction of white dwarfs on the so-called Q branch must experience an extra cooling delay of $\sim 8\,$Gyr not predicted by current models.