Astronomers believe supermassive black holes probably lurk in the centers of most large galaxies. These gargantuan black holes can gather swirling disks of material around them as their gravity attracts stars and gases. In some cases, these disks can emit vast amounts of light and even shoot huge jets of matter into space. The center of such an eventful galaxy is called an active galactic nucleus, or AGN.
Our own Milky Way seems to have a relatively calm center, but astronomers suspect this wasn’t always the case.
Some clues suggest that a flare of energetic radiation burst from our galaxy’s center within the last few million years. Now, in a new study, a team of researchers describes another piece of evidence that the Milky Way burped out such a flare. The research also points to the supermassive black hole in our galaxy’s center, called Sagittarius A* or Sgr A*, as the responsible party.
The team also estimated when this event occurred. Their data put the outburst at 3.5 million years ago, give or take a million years. That would mean that the Milky Way’s center transitioned from an active to a quiet phase pretty recently in Earth’s history, possibly when early human ancestors were roaming the planet.
The flare would have been visible to the naked eye, shining about 10 times fainter than the Full Moon across a broad spectrum of light wavelengths.
“It would look like the cone of light from a movie projector as it passes through a smoky theater,” University of Sydney astrophysicist and lead study author Jonathan Bland-Hawthorn said in an email.
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