The supermassive black hole in the center of the Milky Way is usually quiet, but in May it surprised astronomers with an unprecedented burst of infrared light.
A supermassive black hole near the Earth, called Sagittarius A * or Srp A *, suddenly became 75 times brighter than normal near the infrared region of the light spectrum for two hours on May 13, a team of scientists has found.
According to a new document published on 5 August in arXiv, Cornell University's repository of scientific works that have not yet been reviewed, this is the brightest flash scientists have seen in 20 years of observing a black hole – and twice as bright as any previously recorded.
"The black hole was so bright that I initially mistook it for the S0-2 star, as I had never seen Sgr A * so bright," Tuan Do, an astronomer and lead author of the paper, told ScienceAlert. "I almost realized that something interesting was happening to the black hole."
The new findings "push the boundaries of current statistical models" because they do not read infrared levels so high and suggest that scientists understand the central black hole of our galaxy is out of date, a team wrote in the paper.
Scientists believe that each galaxy has a particularly dense "supermassive" black hole at its center. The proximity of Sgr A * makes it the easiest black hole for scientists to explore. The team, who discovered this unprecedented blast, monitored Sgr A * for four nights with an infrared camera at Mauna Kea's Keck Observatory in Hawaii.
They hoped to test Albert Einstein's theory of general relativity by observing how a black hole distorts the light of a nearby star. They got what they came for, plus the unprecedented infrared glow.
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For three of the four nights of observation, the black hole was in a "clearly elevated state", writes Do.
"We think something out of the ordinary can happen this year, as it seems that the black hole differs more in brightness, reaching brighter levels than we have ever seen in the past," said Do.
But researchers are not sure exactly what is going on.
In black holes, matter accumulates in a small space, which gives them extremely powerful gravity – Sgr A *, for example, has a mass of 4 million suns. The pull of a black hole is so intense that even light cannot escape, so researchers must observe the infrared or X-ray light emitted from the black hole and interact with nearby gases and stars.
Researchers believe that such an interaction could cause this bright flash. Specifically, they said, an interaction with a nearby star past close to Sgr A * in 2018 could disrupt gas flows at the end of the black hole's grasp.
They also pointed to a dust cloud that passed through Sgr A * in 2014 but did not break as dramatically as astronomers thought it would. Brightness can be a "slow reaction," they wrote.
In 2013, scientists discovered an equally mysterious X-ray flash of Sgr A * that is 400 times brighter than their normal levels of X-ray radiation.
Scientists must continue to monitor Sgr A * to see if it is undergoing significant changes, writes Do. More research can also be used to update the patterns of regular flow at black hole radiation levels.
"Many astronomers have been observing Sgr A * this summer," Do. "I hope to get as much data as possible this year before the region of the sky with Sgr A * gets behind the sun and we won't be able to watch it again until next year."