‘Unprecedented’ bright light flashes from closest supermassive black hole to Earth leaving astronomers baffled

Katy Clifton

A mysterious light brighter than astronomers have seen before has been spotted flaring from the closest supermassive black hole to Earth.

The massive burst of light was seen flashing from Sagittarius A* (Sgr A*), which is situated in the middle of the Milky Way, 26,000 light-years from Earth, and astronomers are not sure what caused it.

During observations over four days in April and May, astronomers recorded “unprecedented near-infrared brightness and variability” of the supermassive black hole.

While Sgr A* has been known to be “highly variable” for several years, the bright light is said to have flashed to over 75 times the normal amount for a few hours.

Time-lapse images shared on Twitter show the bright lights flashing from the black hole.

A study published in Astrophysical Journal Letters last week said: “The electromagnetic counterpart to the Galactic center supermassive black hole, Sgr A*, has been observed in the near-infrared for over 20 years and is known to be highly variable.

“We report new Keck Telescope observations showing that Sgr A* reached much brighter flux levels in 2019 than ever measured at near-infrared wavelengths.”

The study added that astronomers observed “a factor of 75 change in flux over a two-hour time span”.

Sharing time-lapse images of the black hole, astronomer at University of California Tuan Do wrote on Twitter: “The black hole is always variable, but this was the brightest we've seen in the infrared so far.

“It was probably even brighter before we started observing that night.”

Although scientists are yet to determine why the flash happened, Mr Do told Science Alert the flash could have been caused by another star passing close by.

He also said the flash could have taken place due to a delayed reaction to a gas cloud, which passed close to Sgr A* in 2014.

Mr Do added: “The brightness variations come from the light of hot gas falling towards the black hole, before it crosses the event horizon.

“The black hole itself doesn't emit light. Increased activity is probably related to changes in the gas flow. Big questions: why? How long will this last?”