Topic summary
White dwarfs
Extracted from the Wikipedia article White dwarf.
Stars with low to medium mass
White dwarfs with a mass greater than 1.05 M☉ are termed ultramassive white dwarfs. When formed in single-star systems, these are expected to have an oxygen-neon core. However, a significant fraction (~20%) of ultramassive white dwarfs are formed through white dwarf mergers. In this case the result is a carbon-oxygen ultramassive white dwarf.