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Astronomers Spy a Black Hole’s Double ‘Burp’

New observations suggest that black holes cycle between activity and rest

(J Comerford/ESA/NASA)
smithsonian.com

Black holes are notoriously messy eaters, blasting the scraps of shredded stars as enormous belches of gas and dust. Now, for the first time, astronomers spotted the same black hole letting out two hearty burps.

"Black holes are voracious eaters, but it also turns out they don't have very good table manners," astronomer Julia M. Comerford said during a news conference at the American Astronomical Society's winter meeting, Sarah Lewin reports for Space.com. "We know a lot of examples of black holes with single burps emanating out, but we discovered a galaxy with a supermassive black hole that has not one but two burps."

It’s not uncommon for astronomers to observe the aftermath of a black hole guzzling down a star—while most of the material is lost behind its event horizon (what Lewin aptly calls the "point of no return"), traces of its meal are burped out in high-energy jets of particles that are blasted into space. Astronomers have long theorized that supermassive black holes—the black holes millions to billions times the mass of the sun that lurk in the center of galaxies—go through periods of activity and quiescence, a cycle of feeding and naps over enormous timescales.

Now, a team of researchers led by Comerford have witnessed the supermassive black hole at the center of galaxy about 800 million light-years from Earth emitting these jets twice, the scientists write in an article for The Astrophysical Journal. The Hubble Space Telescope imaged the black hole in visible light and the Chandra X-ray Observatory scanned it using X-rays. The space telescopes captured two gas bubbles shocked by jets of fast-moving particles.

One was a cloud of blue-green gas. It was ionized, meaning its electrons were stripped from its atoms, Paul Rincon reports for BBC, which suggests that the cloud was blasted by radiation from the black hole. Researchers measured the cloud lingering some 30,000 light-years from the black hole, and during its lengthy time of traveling the "burp" had plenty of time to expand.

The younger burp, however, is a small loop that’s only 3,000 light-years from the black hole, Lewis writes. The two clouds were the result of two different feeding episodes for the black hole with a 100,000 year resting period in between. The long period between events matches computer models of how black holes feed, Lewis reports.

"Imagine someone eating dinner at their kitchen table and they're eating and burping, eating and burping,” Comerford​ tells Ricon. "You walk in the room and you notice there's an old burp still hanging in the air from the appetizer course. Meanwhile, they're eating the main course and they let out a new burp that's rocking the kitchen table."

The same situation could be happening with Sagittarius A*, the supermassive black hole in the center of our home Milky Way galaxy. "Right now, our galaxy's supermassive black hole is firmly in the nap phase of the feast-burp-nap cycle, but it's just waiting for its next meal to come along," Comerford tells Lewis. "In the future, it will probably feast and burp once again."

While high-energy jets emerging from black holes can be dangerous to anything nearby, the solar system is sufficiently on the outskirts of the Milky Way, so we won't be at risk if Sagittarius A* awakens for a snack.

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