An ultramassive white dwarf half Earth's size may hold a rare oxygen-neon core

Astronomers found that an ultramassive white dwarf, SDSS J0608−0059, likely holds a rare oxygen-neon core. A team led by Stefan M. Arseneau of Boston University studied the star to understand its composition. This discovery, published in The Astrophysical Journal, showed that such heavy stars evolve differently than typical carbon-oxygen white dwarfs.