Scientists once believed that at the core of the Milky Way galaxy lay “a sleeping monster” that weighed 4 million times our sun’s mass.
They’re referring to a black hole, a region “in space where gravity pulls so much that even light cannot get out.”
But now that may not be the case, according to findings published in the Astrophysical Journal on Dec. 6.
Researchers from the University of North Carolina at Chapel Hill found that the Milky Way’s supermassive black hole periodically awakens to consume a star or gas cloud that falls into it, NASA said in a news release.
Gerald Cecil, the university’s physics and astronomy professor, suggests “the black hole burps out mini-jets every time it swallows something hefty, like a gas cloud,” according to the news release.
The jets are streams of energy and hot matter that escape from the black hole and travel at nearly the speed of light, NASA said.
The Hubble Space Telescope found “circumstantial evidence that it (the jet) is still pushing feebly into a huge hydrogen cloud and then splattering, like the narrow stream from a hose aimed into a pile of sand.”
Pieces of this “blowtorch-like jet” date back several thousand years, but since Hubble wasn’t able to take photographs, Cecil relied on observations.
Black holes consume anything massive
Cecil’s curiosity was piqued when research from 2013 revealed a southern jet near the black hole shooting out gas, according to the news release.
Using data Hubble and the Atacama Large Millimeter/Submillimeter Array Observatory in Chile, Cecil looked for traces of a northern counter-jet.
Although observations from the telescope in Chile revealed a narrow linear feature extending 15 light-years into the molecular gas cloud from the black hole, the Hubble images showed a glowing, inflating bubble of hot gas that extends at least 35 light-years from it.
His findings suggest that the black hole expels mini-jets when it devours a gas cloud or anything massive. In return, the interaction between the jet and the surrounding hydrogen gas inflates the bubble.
Cecil and co-author Alex Wagner from Tsukuba University in Japan then recreated their findings using supercomputer models of stimulated jet outflows.
“Like in archaeology, you dig and dig to find older and older artifacts until you come upon remnants of a grand civilization,” Cecil told NASA.
The explosive outburst’s tie to the Milky Way
Cecil used his observations from the Hubble telescope and “radio images of another galaxy with a black hole outflow” to better understand the explosive outburst.
He found that spiral galaxy NGC 1068, located 47 million light-years away, “has a string of bubble features aligned along an outflow from the very active black hole at its center” — and has similar features to the Milky Way.
“NGC 1068 may be showing us what the Milky Way was doing during its major power surge several million years ago,” Cecil said in the news release.
The Milky Way’s black hole had an explosive outburst about 2 to 4 million years ago that created a massive pair of bubbles that glow above our galaxy, according to NASA.
“Our central black hole clearly surged in luminosity at least 1 millionfold in the last million years,” Wagner told NASA.
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