Astronomers have spotted strange flashes coming out of the Milky Way’s central black hole, the Sagittarius A*. It became 75 times brighter.
The giant swirling beast at the center of our galaxy is four million times the mass of the Sun. A team of scientists has been measuring it for over 20 years.
Back in May, UCLA astronomer Tuan Do and his colleagues were observing Sgr A* using the Keck Telescope on the summit of Mauna Kea in Hawai’i. They observed unusual blasts of radiation coming out of it. The flash of infrared radiation was more powerful than ever.
In a period of just two hours, they witnessed the black hole become 75 times brighter.
Here’s a timelapse of images over 2.5 hr from May from @keckobservatory of the supermassive black hole Sgr A*. 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! pic.twitter.com/MwXioZ7twV— Tuan Do (@quantumpenguin) August 11, 2019
Describing the discovery in a new paper published in Astrophysical Journal Letters, the researchers say the chance of seeing such a series of blasts being sent through the galaxy is very low, after calculating it using “the most comprehensive statistical model ever published”.
The chance of seeing one night with this kind of radiation is 0.3 percent, the researchers say. The chance of seeing unusual activity over four nights, as the researchers did, is less than 0.05 percent.
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The researchers suggest the flashes could indicate that our central black hole has become more active, or that it has started accreting more or different material.
Once the black hole starts eating nearby objects like stars or dust clouds, the infalling material heats up at the event horizon, therefore lighting up the region. Even though the gravitational field there warps space to the point that light can’t escape, telescopes can still pick up the radiation coming out of the event horizon.
However, the sudden flash could also mean that our understanding of the black hole is not correct and that researchers will have to come up with a new model to understand it.
But astronomers speculate that the flash was thrown out when a star known as S0-2 moved close to the black hole, in 2018. That close pass may have disturbed gases at the event horizon enough to cause the flashing event.
Another reason might be a cloud of dust known as G2 which passed about 36 light-hours from Sgr A* in 2014.
However, more observations might shed light on this mystery.