Researchers at the University of Warwick report finding a white dwarf barreling through space at great speed. The source, they say, was likey a “partial supernova” which ejected the core of the star.
Image credits University of Warwick / Mark Garlick.
Sitting at about 40% the mass of our sun, white dwarf SDSS J1240+6710 is much smaller, and denser. Data from the Hubble telescope allowed researchers to confirm that its atmosphere is an unusual mix of gases.
A peculiar star
“There is a clear absence of what is known as the ‘iron group’ of elements, iron, nickel, chromium and manganese,” explains a statement from the University of Warwick.
“These heavier elements are normally cooked up from the lighter ones and make up the defining features of thermonuclear supernovae.”
White dwarfs are born when a star completely consumes its fuel. Most of its mass blows away to form a nebula, leaving behind a white-hot core. They usually have atmospheres consisting of hydrogen or helium, the researchers add, with traces of carbon and oxygen produced as the star grew old.
This particular one, however, was made from oxygen, neon, magnesium and silicon. Furthermore, the lack of elements in the iron group points to it undergoing a “partial supernova” before it died. Heavier elements are formed by light atoms being pushed together in stars as they explode.
Its speed — this solar remnant is travelling at around 559,234 mph — would indicate that it was thrown out in the event.
“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,” says Professor Boris Gaensicke from the Department of Physics at the University of Warwick, lead author of the paper.
“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.”
The paper “SDSS J124043.01+671034.68: the partially burned remnant of a low-mass white dwarf that underwent thermonuclear ignition?” has been published in the journal Monthly Notices of the Royal Astronomical Society.