Red flashes reveal black hole feeding on star

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The binary system V404 Cygni was emitting powerful red flashes

Astronomers believe the flashes are from a black hole spewing out star material

CNN  — 

Rare and powerful flashes from a black hole consuming a star have been observed by astronomers.

These flashes are some of the brightest black hole outbursts seen in recent years, according to a new study published in the journal Monthly Notices of the Royal Astronomical Society.

In June 2015, V404 Cygni, a binary system that is comprised of a black hole and an orbiting star slightly smaller than the sun, went through a phase of dramatic brightening for two weeks.

During the brightening, strong red flashes of light lasting only fractions of a second were observed as the black hole devoured material from its companion star.

NASA’s Swift satellite also detected a rising tide of high-energy X-rays from the constellation Cygnus, which is about 8,000 light years from Earth.

A fast-imaging camera that was mounted on a telescope in the Canary Islands documented the flashes. These blinding flashes were about the output of a thousand suns and some flashes lasted for a short period, about 10 times faster than the blink of an eye.

A team of international scientists from Europe, the United States, India and the United Arab Emirates led by the University of Southampton in England, reported that the red flashes are coming from star material that was not consumed by the black hole and was essentially spewed out into space.

A movie of fast red flashes from V404 Cygni observed by the ULTRACAM fast imager on the William Herschel Telescope in the early morning hours of June 26, 2015.

Astronomers have described these red flashes as fast-moving jets of matter. It’s an interesting phenomenon because black holes are so dense, not even light can escape their gravity.

“The very high speed tells us that the region where this red light is being emitted must be very compact,” lead author of the study Dr. Poshak Gandhi said in a press release.

A black hole, which typically forms from the remnants of a dying star that has gone through a supernova explosion, can be imagined as a great amount of matter squeezed into a very small area.

“These red flashes were found to be strongest at the peak of the black hole’s feeding frenzy,” Gandhi said.

Astronomers theorize that when the black hole was rapidly force-fed by its companion star, it reacted violently, spitting out parts of the star’s material as a fast-moving jet.

“The duration of these flashing episodes could be related to the switching on and off of the jet, seen for the first time in detail,” Gandhi said.

These black hole outbursts are so rare and unpredictable that scientists are typically caught off guard by the event. For instance, the last time V404 Cygni was erupted was in 1989.

Most outbursts are relatively dim, but the flashes from V404 Cygni have been some of the strongest to be observed in recent years.

“The 2015 event has greatly motivated astronomers to coordinate worldwide efforts to observe future outbursts,” Gandhi said.