Black Holes Could Be Major Power Source

Date:10 September 1999

Black holes, those invisible matter-sucking drains thought to lurk in galaxies' hearts, may be the force behind half the energy released since the universe began, scientists reported on Friday.

Astronomers have presumed for years that black holes emitted a bit of energy, but nothing like the monstrous power spewed by stars. This latest research means that black holes could give stars serious competition on the cosmic power grid.

``Up to now, the thinking was that in the visible universe, all the energy has been released from the center of stars,'' said Nicholas White of NASA's Goddard Space Flight Center in Maryland.

``This new research suggests that there's a lot more energy being released and it's been hidden by dust and gas,'' White said in a telephone interview from Bologna, Italy, where he chaired a meeting on X-ray astronomy.
Black holes are high-gravity regions of space that suck in every bit of matter they can grab, not even letting light escape. First postulated in theory early in this century, black holes have been the subject of intense study in recent years, and new data have erased most doubts about their existence.

Because they cannot be seen, black holes have always retained a certain mystery. In fact, much of the power they emit can only be traced through X-rays, according to Andrew Fabian of the University of Cambridge, who presented his research about black holes' energy output at the X-ray meeting.

ENERGY FROM SWIRLING GAS

There are several varieties of black holes. Fabian focused on massive ones, which may contain the mass of millions or even billions of suns packed into a region the size of our solar system. He and others have found that energy is produced as gas swirls into the black hole, gaining tremendous speed and heat as it nears the point of no return.

This hot, fast-moving gas emits lots of radiation, ranging from optical light to X-rays, before being gobbled up. Until recently, only the optical light could be discerned.

The advent of new X-ray astronomical instruments, including the new Chandra observatory, will either prove or disprove Fabian's theory in the near future, White said.

Steve Maran, assistant director of space science at NASA's Goddard center, said further study is needed.

``The big issue is whether the black holes really provide half the energy released in the universe, or a lesser amount,'' Maran said by telephone. ``Just the fact that this is a serious possibility shows how giant black holes have gone from hypothetical objects to possible major players in the universe as we understand it.''

The total energy produced by stars and black holes does not include the energy emitted in the theoretical Big Bang the scientists believe created the universe.