Astronomers find black hole destroying a star

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Astronomers find black hole destroying a star

2011-08-25 09:33:21 GMT+7 (ICT)

WASHINGTON, D.C. (BNO NEWS) -- Astronomers have been able to spot a previously dormant black hole from a distant galaxy as it shredded and consumed a star, NASA said on Wednesday.

The incident has been streaming X-rays toward Earth since late March, and NASA's Swift satellite, which launched in November 2004 and is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland, first alerted astronomers to intense and unusual high-energy flares from the new source in the constellation Draco.

David Burrows, professor of astronomy at Penn State University and lead scientist for the mission's X-Ray Telescope instrument, said that the source, known as Swift J1644+57, could produce bright X-rays enough for Swift to observe into next year. The galaxy in which the black hole is located, however, is so far away it took the light from the event approximately 3.9 billion years to reach Earth.

Burrows' study, which included scientists from NASA, highlights the X- and gamma-ray observations from Swift and other detectors, including the Japan-led Monitor of All-sky X-ray Image (MAXI) instrument aboard the International Space Station (ISS).

In a second study, Ashley Zauderer, a post-doctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, examines the unprecedented outburst through observations from numerous ground-based radio observatories, including the National Radio Astronomy Observatory's Expanded Very Large Array (EVLA) near Socorro, New Mexico.

A central supersized black hole weighing millions of times the sun's mass is usually present in most galaxies, including the Milky Way. According to both studies, the black hole in the galaxy hosting Swift J1644+57 may be twice the mass of the four-million-solar-mass black hole in the center of the Milky Way galaxy.

As a star falls toward a black hole, it is ripped apart by intense tides. The gas is corralled into a disk that swirls around the black hole and becomes rapidly heated to temperatures of millions of degrees.

On March 28, flares were first detected, but they were initially assumed to signal a gamma-ray burst, one of the nearly daily short blasts of high-energy radiation often associated with the death of a massive star and the birth of a black hole in the distant universe.

However, as the emission continued to brighten and flare, astronomers realized that the most plausible explanation was the tidal disruption of a sun-like star seen as beamed emission.

EVLA observations by Zauderer's team showed a brightening radio source centered on a faint galaxy near Swift's position for the X-ray flares just two days later. These data provided the first conclusive evidence that the galaxy, the radio source and the Swift event were linked.

"Our observations show that the radio-emitting region is still expanding at more than half the speed of light," said Edo Berger, an associate professor of astrophysics at Harvard and a coauthor of the radio paper. "By tracking this expansion backward in time, we can confirm that the outflow formed at the same time as the Swift X-ray source."

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