Astronomers hear ‘death cry’ of star shredded by black hole

A team of astronomers has detected the “death cry” of a star being devoured by a supermassive black hole. The black hole had been sitting quietly — almost lying in wait, as it were — until its gravity reached out and shredded a passing star, pulling the star into its death grip and causing it to emit a characteristic signal. “You can think of it as hearing the star scream as it gets devoured, if you like,” said astronomer Jon Miller of the University of Michigan, lead author of a report appearing in Science Express.

The black hole, identified as Swift J1644+57, lies 3.9 billion light-years away in the constellation Draco. That name arises from its discovery on March 28, 2011, by NASA’s Swift satellite, which searches the universe for gamma-ray bursts. At first, astronomers thought the signal was a common gamma-ray burst, but the gradual fade-out of the signal matched nothing that had ever been seen before from such a source. Closer observation of the object with the orbiting Suzaku and XMM-Newton X-ray telescopes ultimately revealed a faint, periodic signal that, Miller said, corresponds in frequency to an ultra-low D-sharp.

Such signals have been detected from smaller black holes and they are thought to emanate from material that is about to be sucked in, said co-author Rubens Reis of the University of Michigan. But a similar signal had previously been detected only once from a supermassive black hole — one with a mass more than a million times that of the sun — in a galaxy just576 million light-years away.

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