Black Holes Are "Green," X-Ray Study Says

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Christopher Reynolds, an astronomer and study co-author at the University of Maryland in College Park, explained that quasars are considered more exciting because the material that falls into them is converted into bright light.

"This is what makes them powerful beacons of light that can be viewed across most of the observable universe," he said during the briefing.

The older supermassive black holes, Reynolds and Allen had observed, were not generating as much radiation—light, x-rays, et cetera—as would be expected from the amount of material falling toward them.

The team's study of these black holes, however, revealed these black holes are "extremely efficient not at producing light but at driving powerful jets," Reynolds said.

"So we've shown that black holes never seem to lose their efficiency at converting matter into energy, they just put energy out in different ways in different phases."

According to Reynolds, these older black holes, each about a billion times more massive than our sun, release about a thousand times more energy as jets rather than as light.

Measuring Efficiency

To find out how efficient the supermassive black holes are, the researchers first used Chandra images of the central regions of elliptical galaxies to estimate the amount of fuel available for the black hole.

The team then used Chandra images to measure the size of the bubbles created by the jets and the jet power.

"So putting these results together—the fueling rates and the jet power—we measure an efficiency for these black-hole engines that goes far beyond any engine we are used to here on Earth," Allen said.

According to Allen, the study represents the first direct measurement of black hole fuel efficiency.

Exactly why these older, supermassive black holes are so efficient at making these jets will require further study, Reynolds added.

"But that's great. This is just part of the learning process by which we learn how these fascinating complex objects work."

A paper on this research will appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.

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