Cosmic cannibalism involving a black hole and a star has been considered as a rarity until now, but a new study has shown that these events are not so rare and they happen all the time in our vast Universe.
Researchers at University of Sheffield and colleagues say that a black hole devouring a star has always been seen as an event that happens extremely rarely. Surveys of galaxies have revealed that it happens once ever 10,000 to 100,000 years per galaxy. But that’s not the case say researchers at the University who found that supermassive black holes rip up and devour hapless stars a hundred times more frequently than thought.
Black holes consuming stars is said to be “tidal disruption events” and these have only been witnesses very few times in astronomical surveys canvassing tens of thousands of galaxies. But the authors of a new study said they spotted a star being destroyed by a black hole in a survey of only 15 galaxy collisions – an extremely small sample size by astronomy standards. The chances of a star disappearing into the maw of a black hole go up a hundredfold when galaxies crash, they concluded. The probability of a black hole ripping apart a star and swallowing it increases by manyfolds when two galaxies collide.
Supermassive black holes are millions to billions times more massive than our Sun. Astronomers agree they reside at the centre of almost all known major galaxies. The Milky Way’s own black hole – currently dormant – is tucked inside the constellation Sagittarius. But exactly how these monsters form is still hotly debated among scientists.
For the new study, a team led by astronomer Clive Tadhunter, also from Sheffield, analysed 15 colliding galaxies, each containing billions of stars. In 2015, they noticed a startling change in one of them – galaxy F01004-2237, some 1.7 billion light years from Earth – compared to a decade earlier. Sifting through historical data collected by the Catalina Sky Survey, the researchers traced the transformation to 2010. The brightness flared that year in a way consistent with the death throes of a star being ripped apart. Once in the danger zone, the doomed star is sucked in by a black hole’s gravitational pull.