Black Hole at Heart of Milky Way Keeps Flashing and No One Knows Why

Sagittarius A* keeps flashing randomly on a daily basis. Astronomers mapped 15 years of radiation bursts to try to figure out why.
John Loeffler

The supermassive black hole at the center of the Milky Way, Sagittarius A*, keeps releasing random bursts of radiation on a daily basis and no one can figure out what is causing it. Now, an international team of researchers compiled 15 years of data to try and solve the mystery.

The team, led by a postgraduate student named Alexis Andrés, mapped a decade and a half's worth of gamma-ray bursts from Sagittarius A* using NASA's Neil Gehrels Swift Observatory.

These bursts ranged from tens to hundreds of times brighter than the normal signals sent out by the supermassive black hole at the heart of our galaxy, but they don't appear to follow a discernable pattern.

The data from 2006 to 2008 show high levels of gamma-ray activity, followed by a rapid four-year-long drop, after which activity shot back up, starting in 2012.

There could be any number of reasons for the irregularity in the bursts, including gaseous clouds or stars passing between us and A* that is partially blocking the radiation.

The research team hopes that data in the next few years can help narrow down the list of astronomical suspects and even reveal the ultimate cause of these mysterious bursts.

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"How the flares occur exactly remains unclear," said Dr. Jakob van den Eijnden, of Oxford University, who is one of the co-authors of the study published in the Monthly Notices of the Royal Astronomical Society.

"It was previously thought that more flares follow after gaseous clouds or stars pass by the black hole, but there is no evidence for that yet. And we cannot yet confirm the hypothesis that the magnetic properties of the surrounding gas play a role either." 

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