No, it's not a Stephen King novel set in space: scientists are calling a white dwarf star a ‘cannibal’ because it probably ingested the surrounding planets and asteroids it was born with – leaving it with a tell-tale scar.
For the first time ever, researchers have spotted a unique clue on the white dwarf to solve this case: a trace of metals on its surface.
“Nothing like this has been seen before,” said the study’s co-author John Landstreet, a professor at Western University, Canada. The results of the observation have been published in The Astrophysical Journal Letters.
Known as WD 0816-310, the white dwarf is now an Earth-sized remnant of a star that was previously as big as our Sun.
The researchers behind the study spotted it using the European Southern Observatory’s Very Large Telescope (VLT) in Chile. A concentration of metals makes up the cannibal star's scar, which the scientists detected using a ‘Swiss-army knife’ instrument known as FORS2 on the VLT.
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The researchers theorise that when planets and asteroids approached the white dwarf, they dismantled and formed a ring of debris around the dead star. WD 0816-310 then devoured parts of this ring, leaving traces of certain chemicals on its surface – a bit like the sticky evidence of a food theft left all around a child’s mouth.
But the scientists noticed something else. When observing the star, they spotted that the strength of metal detection changed as the star rotated, in a similar way to how its magnetic field changed.
They realised that the magnetic fields were funnelling these metal elements onto the cannibal star and concentrating them at its poles – which is where the 'scar' formed.
The results of the observation will help scientists learn more about the composition of exoplanets. They also reveal how stars continue to play active roles in planetary systems even after their ‘death’ – making WD 0816-310 not just a ‘cannibal’ star, but a zombie one too.
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