Image courtesy A. Weiss and R. Kraft, ESO/WFI/MPIfR/APEX/NASA/CXC/CfA

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A composite image of Centaurus A reveals lobes and jets emanating from the galaxy's central black hole.

Image courtesy A. Weiss and R. Kraft, ESO/WFI/MPIfR/APEX/NASA/CXC/CfA

Black Hole Caught Pulling Trigger on Gas "Bullets"

Gas knots seen moving at a quarter the speed of light, astronomer says.

New ultrasharp pictures show the exact instant a black hole launched gigantic, high-speed "bullets" of gas, scientists announced today.

The data come from observations of a black hole called H1743-322 and its companion star, located about 28,000 light-years from Earth.

Black holes in such binary systems can pull material off their companions to form rapidly spinning disks around their equators, called accretion disks. Matter from the disks falling into the black holes can cause them to spew jets of matter from their poles.

Occasionally, though, these steady jets disappear and are replaced by superfast knots of charged gas fired from the black hole "akin to bullets in a gun," said researcher Gregory Sivakoff at the University of Alberta in Canada.

Such outbursts can produce as much energy in an hour as our sun emits in five years.

H1743-322, a black hole about five to ten times the mass of the sun, had generated a number of such outbursts since its discovery in 1977.

Until now, however, astronomers weren't exactly sure when a black hole "pulled the trigger" and unleashed its gas bullets, a key part of understanding why the bullets appear in the first place.

Black Holes Caught in the Act

The scientists captured extremely detailed images of a pair of bright, radio-emitting knots of gas launched in opposite directions from H1743-322 in 2009.

By measuring the motions of these bullets, the scientists were able to work backward and pinpoint when they were hurled outward. (See black hole pictures.)

"We caught it in the act of launching a jet of material at nearly a quarter the speed of light," Sivakoff said.

Changes in H1743-322's x-ray and radio emissions also suggest the black hole bullets may result from blobs of gas in the surrounding disks of material that get destroyed once they spiral too close to the black hole.

"These are first steps toward getting a better understanding of accretion disks and the physics of what launches the jets," Sivakoff said.

The black hole bullets were described Tuesday at the annual meeting of the American Astronomical Society in Austin, Texas.