NASA’s Swift satellite has detected the start of a new X-ray outburst from the binary system V404 Cygni, where a black hole and a Sun-like star orbit each other.
A research team led by Andrew Beardmore at the University of Leicester imaged the system using the X-ray Telescope aboard Swift, revealing a series concentric rings extending about one-third the apparent size of a full moon.
An image, above, shows the expansion and gradual fading of the rings.
Astronomers say the rings result from an “echo” of X-ray light. The black hole’s flares emit X-rays in all directions. Dust layers reflect some of these X-rays back to us, but the light travels a longer distance and reaches us slightly later than light traveling a more direct path. The time delay creates the light echo, forming rings that expand with time.
Detailed analysis of the expanding rings shows that they all originate from a large flare and that there are multiple rings because there are multiple reflecting dust layers between 4,000 and 7,000 light-years away from us.
V404 Cygni is about 8,000 light-years from Earth. Every couple of decades the black hole fires up in an outburst of high-energy light. Its previous eruption ended in 1989.
The investigating team includes scientists from the Universities of Leicester, Southampton, and Oxford in the U.K., the University of Alberta in Canada, and the European Space Agency in Spain.
Bill Condie is a science journalist based in Adelaide, Australia.
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