In new research coming out of Warwick University, an surprisingly large white dwarf has been found in data from the Gaia mission. This system, cataloged as WDJ 0551+4135, appears to be the result of a stellar merger that just squeaked in under the supernova triggering weight limit. And not only was this star made in a stellar merger, but it appears to be the merger of two small white dwarf stars.

Folks, the more we look at the universe, the more weird stuff we’re going to find.

This bloated star was observed in detail by the William Herschel telescope and found to have a surface composition of both Hydrogen and Carbon. While these elements are common on white dwarfs, they aren’t generally found together. Carbon white dwarfs are formed in the deaths of larger stars that start out a few solar masses in size, and hydrogen come from smaller stars. To see both… means both kinds of stars were born and died and merged. And somehow didn’t explode. This star appears to be 1.14 solar masses – twice the average of a white dwarf – and these systems max out and go boom at 1.4 solar masses. This is turning into the academic year when we learn stars just like to merge, and this is a pretty common thing in our universe.

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Two stars merged to form massive white dwarf (Warwick U)