Telescope sees black hole gobbling up matter

SEATTLE -- The supermassive black hole at the center of the Milky Way flares with intense eruptions every day as it gobbles up nearby gas, dust and objects. But the most sensitive X-ray images ever taken show it is starved and puny compared with black holes in other galaxies.

Astronomers using the Chandra X-ray telescope have captured images of intense flares streaking from the center of the Milky Way and said the violence comes from a supermassive black hole living on matter.

The study also suggests that the Milky Way's black hole is underfed when compared with the supermassive black hole of other galaxies, said Frederick K. Baganoff of the Massachusetts Institute of Technology. He presented his study Monday at the national meeting of the American Astronomical Society.

Daily eruptions

Baganoff said the Milky Way's black hole spends much of its time quietly emitting X-rays about equal to all the energy streaming from the sun. But at least once a day the black hole suddenly flares, erupting with X-ray bursts 10 to 45 times more powerful than all the sun's energy. Then it settles down again, all within 90 minutes or less.

"No other supermassive black hole has shown this behavior," Baganoff said. "These frequent, short-duration flares are unique to the supermassive black hole in our galaxy."

Baganoff said the black hole may be starved because nearby star explosions in the past have blown away most of the gas and dust that would feed the black hole.

"Although it appears to snack often, this black hole is definitely on a severe diet," he said.

The black hole swallows mass equal to about one-billionth of the sun every year, but the mass available in the Milky Way suggests it should be sucking in about 100 times more matter.

The Chandra telescope also detected X-rays streaming from clouds and streaks of heated matter that may be the remnants of past meals. As matter is sucked into black hole, some of it is accelerated to near the speed of light and heated to 2 million degrees, flying off away from the galaxy center.

10,000 years ago

Streaks of X-rays just over one light year from the center was probably ejected recently, but other X-rays come from matter that may be been sent streaking away more than 10,000 years ago.

Most galaxies the size of the Milky Way are thought to contain supermassive black holes that form a gravitation center orbited by billions of stars.

Black holes are so dense with mass that their gravity will not allow anything, even light, to escape. They cannot be seen directly because they emit no radiation, but their immense gravity causes matter to spiral at high speeds toward the center, heating the material to millions of degrees and to radiate energy.

The Milky Way's black hole is thought to have about 3 million times the mass of the sun.

Bruce Margon, an astronomer at the Space Telescope Science Institute, said the Chandra X-ray study suggests the Milky Way's black hole is a "messy eater," expelling crumbs from past meals in the form of matter streaking away at high speed. The studies give fundamental new understanding about the behavior and history of black holes in general, he said.

On the Net

American Astronomical Society: www.aas.org