On June 15, 2015, the black hole V404 Cygni experienced an outburst of high-energy light. Since 1989, it had lain dormant. From its position, 8,000 light-years away in the Cygnus constellation, the black hole exhibited activity that was detectable from Earth.
On June 17, astronomers began taking spectroscopic observations of the activity from the 10.4-m Gran Telescopio CANARIAS (GTC), an optical-infrared telescope located in the Canary Islands.
Publishing in Nature, an international team of astrophysicists has reported its detection of x-ray winds traveling at a velocity of 3,000 km/sec near the black hole.
The wind, which originates in the black hole’s outer accretion disk, “is unlike any seen hitherto,” according to the researchers.
“Its presence allows us to explain why the outburst, in spite of being bright and very violent, with continuous changes in luminosity and ejections of mass in the form of jets, was also very brief, lasting only two weeks,” University of Southampton Prof. Phil Charles said in a statement.
During its outburst, the black hole off and on became the brightest object in the x-ray sky, according to NASA. At times, it shined 50 times brighter than the Crab Nebula.
According to the European Space Agency, a binary system like V404 Cygni, which is 10 times the mass of the sun, usually collects material from interstellar space in a disk, where it heats up before spiraling into the black hole.
The researchers wrote that the neutral, outflowing wind (unionized hydrogen and helium) triggered the formation of a nebula, which consisted of the expelled materials by the wind.
“The large expelled mass indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk,” the researchers wrote.
On top of the data from GTC, the researchers used data from the INTEGRAL and SWIFT satellites.
“This outburst of V404 Cygni, because of its complexity and because of the high quantity and quality of the observations, will help us understand how black holes swallow material via their accretion disks,” said Teo Muñoz Darias, a co-author of the study and a researcher at Instituto de Astrofisica de Canarias, in a statement.
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