The scientific team think that indicates the star only went through a partial supernova process, with the nuclear reaction ending before it could finish.
Professor Boris Gaensicke from the Department of Physics at the University of Warwick and lead author said: “This star is unique because it has all the key features of a white dwarf but it has this very high velocity and unusual abundances that make no sense when combined with its low mass.
“It has a chemical composition which is the fingerprint of nuclear burning, a low mass and a very high velocity: all of these facts imply that it must have come from some kind of close binary system and it must have undergone thermonuclear ignition.
“It would have been a type of supernova, but of a kind that we haven’t seen before.”