Planetary scientists have discovered two Earth-sized bodies with oxygen rich atmospheres. However, they are not planets but are actually two unusual white dwarf stars.

The two white dwarf stars SDSS 0922+2928 and SDSS 1102+2054 are 400 and 220 light years from Earth are both the remnants of massive stars that are at the end of their stellar evolution having consumed all the material they had available for nuclear fusion.

Searching within an astronomical data set of the Sloan Digital Sky Survey (SDSS), a team from University of Warwick and Kiel University did indeed discover two white dwarfs with large atmospheric oxygen abundances.

Team leader Dr Boris Gicke of Warwick University said, “These surface abundances of oxygen imply that these are white dwarfs displaying their bare oxygen-neon cores, and that they may have descended from the most massive progenitors stars in that class.”

Most stellar models producing white dwarfs with such oxygen and neon cores also predict that a sufficiently thick carbon-rich layer should surround the core and avoid upward diffusion of large amounts of oxygen. “However, calculations also show that the thickness of this layer decreases the closer the progenitor star is to upper mass limit for stars ending their lives as white dwarfs.

“Hence one possibility for the formation of SDSS 0922+2928 and SDSS 1102+2054 is that they descended from the most massive stars avoiding core-collapse, in which case they would be expected to be very massive themselves.

“However current data is insufficient to provide any unambiguous measure of the masses of these two unusual white dwarves,” Dr Gicke said.

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