Black hole burps up gobbled gas and dust

Astronomers can use belched remnants to study galaxy evolution

black hole and galaxies

COSMIC BRAAAAAP  Ripples of hot gas (blue arcs, inset) race away from an erupting supermassive black hole in the center of NGC 5195 (upper left), a galaxy entangled with its neighbor, the Whirlpool Galaxy (bottom left).

X-ray: NASA, CXC, E. Schlegel/Univ. of Texas et al; Optical: NASA, STScI

KISSIMMEE, Fla.— Supermassive black holes are a lot like toddlers. They’re energetic, often the center of attention — and occasionally spit up their food. A black hole at the core of another galaxy has belched twice in the last 6 million years, leaving a record of these eruptions drifting through intergalactic space.

Two arcs of X-ray light hovering next to galaxy NGC 5195 are the hot remnants of two eruptions from a supermassive black hole at its center, astronomer Eric Schlegel reported January 5 at a meeting of the American Astronomical Society. The arcs are about 3,000 light-years apart and several thousand light-years long. 

The older eruption is plowing a layer of glowing hydrogen gas from the center of NGC 5195, which sits about 26 million light-years away in the constellation Canes Venatici. “It’s the best snowplow of shocked material I’ve ever seen,” said Schlegel, of the University of Texas at San Antonio. He discovered the galactic regurgitation in images from NASA’s Chandra X-ray Observatory.

Supermassive black holes feed from disks of superheated gas and dust. Occasionally the black hole bites off more than it can chew. Then it erupts, blasting material out of the galaxy.

NGC 5195 is entangled with its much larger neighbor, the Whirlpool Galaxy. The two are in the midst of merging into one galaxy, which could feed NGC 5195’s supermassive black hole and drive some of these outbursts, though it’s not clear that the observed blasts arise from this intimate relationship. “Aside from saying it happened twice, you’re not going to get anything profound from knowing there are two,” says Nicholas McConnell, an astrophysicist at the National Research Council in Victoria, Canada. Hyperactive black holes are known to hiccup frequently on their own, though Schlegel thinks that, in this case, the interaction with Whirlpool might be at fault.  

The discharge from NGC 5195 can clarify how much mass the galaxy loses in one of these eruptions, McConnell says. So finding fragments of past expulsions could help researchers understand how the maelstrom around a supermassive black hole affects the evolution of the rest of its host galaxy.

“In the early universe, this sort of thing happened more often,” Schlegel says. NGC 5195 might provide a modern reenactment of a time when young galaxies belched more frequently than they do now. 

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