​Black hole wakes up after 26yr sleep to feast on star companion

The “extraordinary behavior” of a massive black hole in our galaxy, has got astronomers thrilled: After staying dormant for over a quarter of a century, it has suddenly awakened and began actively devouring material from its stellar companion.

The V404 Cygni system, consisting of a black hole and a star, can be found some 8,000 light years away in the Cygnus constellation of the Milky Way. The black hole’s sudden awakening and apparent cravings were first detected on June 15 by the Burst Alert Telescope of NASA's 11-year-old Swift satellite.

Swift’s X-ray optics automatically detected the gamma ray burst from the black hole. An X-ray flare also caught the attention of MAXI (Monitor of All-sky X-ray Image), sensor on the Kibo Japanese Experiment Module of the International Space Station.

The dual detection of the activity sparked an exciting observation campaign, with ESA’s 13-year-old Integral gamma ray observatory joining in the effort on June 17, to witness and record the back hole’s activity at multiple wavelengths.

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Over the past weeks astronomers have observed an “exceptional outburst of high-energy light” as the black hole has continued devouring the material of its companion star, the European Space Agency (ESA) said in a statement about the phenomenon.

“The behaviour of this source is extraordinary at the moment, with repeated bright flashes of light on time scales shorter than an hour, something rarely seen in other black hole systems,” said Erik Kuulkers, integral project scientist at ESA.

“In these moments, it becomes the brightest object in the X-ray sky – up to fifty times brighter than the Crab Nebula, normally one of the brightest sources in the high-energy sky.”

The ESA explains that in the so-called “binary system”, the matter from the satellite star is pulled towards the black hole where it gathers in a disc before being heated up producing ultraviolet and X-ray wavelengths. It is then spirals and disappears into the black hole.

The system has not been so active ever since 1989, and the astronomers community “couldn't be more thrilled,” Kuulkers added.

“Many of us weren't yet professional astronomers back then, and the instruments and facilities available at the time can't compare with the fleet of space telescopes and the vast network of ground-based observatories we can use today. It is definitely a ‘once in a professional lifetime’ opportunity.”