Black Hole Devours Star, Blasts Light Beam at Earth

The flash from one of the biggest and brightest bangs yet recorded originated with a massive black hole at the center of a distant galaxy that appears to have ripped apart a star that wandered too close. Some 3.8 billion years later, astronomers at the University of Warwick observed the resulting powerful beam of energy that made its way to Earth.

The high-energy x-rays and gamma rays emitted by the black hole persisted at an extremely bright level for weeks after the event, with bright flares arising when further chunks of the star apparently fell into the black hole. At optical and infrared wavelengths, the phenomenon is as bright as a hundred billion suns.

An artist’s impression of an errant star about to be ripped apart by a black hole recently located in the heart of the constellation Draco. (Image: University of Warwick/Mark A. Garlick)

“Despite the power of this cataclysmic event, we still only happen to see this event because our solar system happened to be looking right down the barrel of this jet of energy,” said Andrew Levan, lead researcher of the international team of observers.

As described in a recent issue of Science, the source of this event — now known as Swift 1644+57 — is right at the heart of a far-away galaxy, 3.8 billion light-years away, at a spot that would be in the constellation Draco. This conclusion comes from a combination of the most powerful telescopes on the ground and in space, working in tandem to pinpoint this unique and unprecedented event. These include the Hubble Space Telescope, the Chandra X-ray Observatory, the Swift Gamma Burst Mission satellite, and the Gemini and Keck telescopes.

An artist’s impression of formation of two jets of energy formed by the star-eating black hole. (Image: University of Warwick/Mark A. Garlick)

When the Swift spacecraft first detected the flash within Draco, astronomers thought it was a gamma-ray burst from a collapsing star and named it GRB 110328A. On March 31, however, Joshua Bloom of the University of California, Berkeley, sent out an e-mail circular suggesting that it wasn’t a typical gamma-ray burst at all, but a high-energy jet produced as a star about the size of our sun that was shredded by a black hole a million times more massive.

“This is truly different from any explosive event we have seen before,” Bloom said.

Andrew Levan, who has led the team observing Swift 1644+57. (Image: University of Warwick)

The best explanation that fits the size, intensity, time scale and level of fluctuation of the event is that a massive black hole at the very center of that galaxy pulled in a star and ripped it apart by tidal disruption, Levan said. The black hole then created two jets, one of which was pointed straight at Earth.

“It is rare for stars to get very close to the black holes in the center of galaxies, but when they do, they will always come off second best,” said Nial Tanvir of the University of Leicester, the second author of the Science paper.

The event is still going on more than 2½ months later, Bloom said, because as the black hole rips the star apart, the mass swirls around like water going down a drain. The process releases a lot of energy.

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