09 January 2014

Black Hole eats a star in Dwarf Galaxy

Image Caption: A dwarf galaxy is located in the galaxy cluster Abell 1795. Credit: X-ray: NASA/CXC/Univ. of Alabama/W.P.Maksym et al & NASA/CXC

NASA’s Chandra X-ray Observatory has helped astronomers witness the first event of a black hole destroying a star in a dwarf galaxy.

Two independent studies using data from Chandra and other telescopes have led scientists to believe they have found what appears to be a star being consumed by a black hole.

“We can’t see the star being torn apart by the black hole,” Peter Maksym of the University of Alabama in Tuscaloosa, Ala., who led one of the studies, said in a statement. “But we can track what happens to the star’s remains, and compare it with other, similar events. This one fits the profile of ‘death by a black hole.’”

When a star wanders too close to a black hole, it begins to get ripped apart by extreme tidal forces. As the debris falls toward the black hole, an intense X-radiation is produced as the debris is heated to millions of degrees. The X-rays would diminish in a characteristic manner as hot gas spirals inward.

The newly discovered episode of black-hole-induced violence is different because it has been associated with a dwarf galaxy. This object is located in the galaxy cluster Abell 1795, which sits about 800 million lights years away from Earth. The dwarf galaxy contains about 700 million stars, compared to the Milky Way which carries between 200 and 400 billion stars.

The black hole in the dwarf galaxy could be a few hundred thousand times as massive as the sun, making it ten times less massive than our galaxy’s supermassive black hole. This means that this object would be classified as an “intermediate mass black hole.”

“Scientists have been searching for these intermediate mass black holes for decades,” Davide Donato of NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Md., who led a separate team of researchers, said in a statement. “We have lots of evidence for small black holes and very big ones, but these medium-sized ones have been tough to pin down.”

Chandra observed Abell 1795 regularly to help calibrate its instruments, so researchers had an unusually large reservoir of data to sift through for the two studies.

“We are very lucky that we had so much data on Abell 1795 over such a long period of time,” Donato’s co-author Brad Cenko, also of GSFC, said in a statement. “Without that, we could never have uncovered this special event.”

Papers describing the research have been published in the Monthly Notices of the Royal Astronomical Society and The Astrophysical Journal.

Now read: NASA’s Swift discovers 100,000 super-massive black holes till now


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