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Black Hole Snowplow

March 4, 2016

A black hole in the center of a small galaxy appears to be pushing gas and dust away from it. That stops the black hole from growing, while potentially giving birth to new stars.

NGC 5195 is a companion to the Whirlpool galaxy, a beautiful spiral near the end of the Big Dipper’s handle. But NGC 5195 itself is a galactic knot — a small, dense clump of stars surrounded by a lot of dust. It has swept past the Whirlpool, perhaps creating waves that sculpted the galaxy’s beautiful appearance.

That encounter also may have sent clouds of gas and dust falling toward the giant black hole at the heart of NGC 5195. As the material collapsed around the black hole, it was heated to many millions of degrees. Radiation and winds from this hot gas then began pushing back at the infalling gas.

Observations by telescopes on the ground and in space recently revealed two “arcs” of gas around the black hole. One arc is quite hot, while the other is cool. The hot arc appears to be pushing at the cool one — in essence, “snowplowing” gas out of the galactic center.

The discovery isn’t all that surprising. Astronomers have long suspected that galaxies and their central black holes affect each other’s evolution. The black hole pulls in gas and dust, triggering the birth of new stars. But as the black hole grows larger, the material around it gets so hot that it pushes away material that’s farther out — shutting off the process of starbirth.

Script by Damond Benningfield

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