British astronomers have discovered a new type of cannibal star that has gobbled up its companion. They identified a twin-star system where one star has stripped so much material away from the other that it can no longer shine.
Researchers at Sheffield University discovered the hungry star using a high-speed camera called Ultracam which they had developed.
They bolted it onto the UK’s giant William Herschel Telescope on La Palma, pictured, in the Canary Islands, to monitor a star 750 light-years away in the constellation of Sextans.
Dr Stuart Littlefair was able to detect the star’s dead victim as it zipped in front of it. By timing this eclipse, his team showed that this companion is a brown dwarf, only a twentieth the size of the Sun. Such cannibal star systems had long been predicted but never found.
Around half the stars in the sky are systems of two or more stars in orbit around each other. In some of these binary systems, the two stars are so close to each other that they almost touch. Astronomers have long believed that this would mean some stars losing so much material that they would lose the ability to sustain nuclear fusion and burn. The problem was they could not find the stellar cannibals.
Dr Littlefair told me: “The star we found didn’t start off as a brown dwarf. It was originally shining as a star about half the size of the Sun”
He said: “It was beginning to look as if these systems either didn’t exist or were too difficult to find using current telescopes. Finding this system was important because their existence had been predicted for so long but, try as we might, we couldn’t find any of these cannibalised stars”.
He added: “This research not only confirms a long-standing theory but it also shows that we can actually find and study these objects, which will hopefully allow astronomers to learn a lot more about how stars die.”