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Gaping holes. X-rays from hot gas in a cluster of galaxies (left) outline two "supercavities" cleared out by an eruption from a central black hole (artist's view, right).

Gorging Black Hole Makes Its Mark

The most energetic eruption yet found in space illustrates the consequences of a black hole's prodigious appetite. The outburst, still going strong after 100 million years, has blasted two enormous cavities into the hot gas in a distant cluster of galaxies. The stark features—each large enough to swallow 600 galaxies the size of our Milky Way—show that black holes can disrupt starbirth and otherwise influence matter far beyond their host galaxies.

The cavities appear in an ordinary-looking group of galaxies about 2.6 billion light-years away. At the center of the cluster resides a supermassive galaxy, bloated by billions of years of consuming smaller galaxies. Radio images had revealed a classic double-sided jet of energy streaming away from this central galaxy. Astronomers assumed that a large black hole inside the galaxy gorged on infalling gas, spouting powerful jets into space from the superhot region close to the hole.

In the new study, NASA's Chandra X-ray Observatory exposed gigantic voids in the hot gas that pervades the cluster, excavated by the fierce jets. The size of each void reveals how hard the black hole had to work to blow away the gas, in the same way that your lungs need to exert more force to inflate a larger and larger balloon. These supercavities are "the most direct possible" measure of the energy released by the black hole's ravenous appetite, says astronomer Brian McNamara of Ohio University in Athens, lead author of the study in the 6 January issue of Nature. Indeed, to shove aside such vast volumes of gas, the jets have churned out as much energy as nearly a billion gamma-ray bursts—the most powerful instantaneous explosions known.

According to the team's calculations, the black hole has driven the jets by devouring an average of three times the mass of our sun each year for the last 100 million years. That rate is similar to the feeding frenzy that powered quasars at the cores of galaxies in the early universe, but it's unheard of in modern galaxies, McNamara says.

"Seeing this huge amount of energy was quite surprising, one might even say shocking," says astrophysicist Richard Mushotzky of NASA's Goddard Space Flight Center in Greenbelt, Maryland. The eruption shows how blazing energy from the centers of galaxies can heat up huge clouds of gas and prevent new stars from forming quickly, he adds. "For the first time, you're actually seeing the energy injected and the gas being heated. We're all really excited."

Related sites
Abstract of paper, with link to full text
Chandra X-ray Observatory, with animations of eruption
Short primer on supermassive black holes