Featured Image: To Heat a White Dwarf

Some astronomical mysteries are found deep in the interiors of stars. Such is the case with the puzzle of Q-branch white dwarfs, a population of these evolved, dense stars that seems to have an unexpected heat source, causing them to cool more slowly than a typical white dwarf. One hypothesis proposes that Q-branch white dwarfs gain extra heat from the rapid sedimentation — sinking to the center of the star — of neutron rich neon, 22Ne. But recent molecular dynamics simulations conducted by Matt Caplan (Illinois State U.), Charles Horowitz (Indiana U.), and Andrew Cumming (McGill U., Canada) show that the tiny crystals of neon needed to speed up this sedimentation can’t exist in a stable state in the interior of a typical white dwarf — which means there must be some other mechanism at work heating Q-branch white dwarfs. The image above shows the initial state of the authors’ simulations, in which a 22Ne microcrystal (red) lies within a soup of carbon and oxygen (white) under the dense, high-pressure conditions that exist inside a white dwarf. To read more about the authors’ work, check out the article below.


“Neon Cluster Formation and Phase Separation during White Dwarf Cooling,” M. E. Caplan et al 2020 ApJL 902 L44. doi:110.3847/2041-8213/abbda0