WASHINGTON: A NASA satellite has detected a brief, super-bright, high-energy flare, an X-ray nova, erupting from a star system 8,000 light-years away from Earth named V404 Cygni.
This system is in the constellation Cygnus and includes a black hole and a star just slightly smaller than the Sun. This black hole has been known to burp up an X-ray nova occasionally, but it had been slumbering since 1989 until the detection by NASA’s Swift Gamma-ray Burst Explorer on June 15.
Relative to the lifetime of space observatories, these black-hole eruptions are quite rare and so, when they see one of them flare up, they try to throw everything they have at it, monitoring across the spectrum, from radio waves to gamma rays, said Neil Gehrels, Swift’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
At the heart of this eruption is the V404 Cygni system, which astronomers classify as a low-mass X-ray binary. In V404 Cygni, a star slightly smaller than the Sun orbits a black hole 10 times its mass in only 6.5 days.
The close orbit and strong gravity of the black hole produce tidal forces that pull a stream of gas from its Sun-size companion star. The gas travels to a storage disk around the black hole and heats up to millions of degrees, producing a steady stream of X-rays as it falls inward.
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