Light ‘outbursts’ from star orbiting black hole observed with naked eye, say researchers


Researchers have succeeded in observing with the naked eye blinking “outbursts” of light from a star orbiting around a black hole, Kyoto University said Thursday.

Light from such a star sometimes grows brighter in what scientists call “outbursts,” and its blinking has been detected only by X-ray equipment.

According to the university, Mariko Kimura and colleagues on a science research course, who have been monitoring V404 Cygni, a binary system comprising a black hole and an orbiting stellar companion, called on researchers in 14 countries to observe the system using 35 telescopes after an outburst was observed there for the first time in 26 years last June.

V404 Cygni is located some 7,800 light years away. The black hole is one of the closest to Earth.

Their 18-day visible observation found the companion star turned brighter than usual, registering an 11th visual magnitude rather than a previous 18th.

A star of the 11th magnitude can be seen with a telescope. In addition, they observed optical variations on timescales from 45 minutes to 2 hours.

An outburst is caused by a nearby star’s gas flowing toward a black hole, gathering in a disc and shining brightly at optical, ultraviolet and X-ray wavelengths before spiraling into the black hole.

The extraordinary phenomenon happens only in a black hole binary system, according to an expert.

“In the future, you may be able to see a star being shone by light from a black hole with the naked eye at an observatory,” Kimura said.