Peering into the 'event horizon' of a black hole

The Chandra X-ray Observatory, a $1.5 billion telescope launched last July, is transmitting pictures that scientists say are changing the way they think of space.

"I've seen maybe 50 images.... There was something I didn't expect to see in maybe half of those," says Harvey Tananbaum, director of the Chandra X-ray Observatory Center in Cambridge, Mass. "Almost everything we looked at is startling."

The most recent discovery is 3C295, a massive collection of galaxies that contains several times the mass of the Milky Way and is 2 million light-years in diameter. The gas cloud around the galaxies is more than 50 million degrees and only visible with an X-ray telescope. Moreover, its previous galactic explosions may have been caused by an excess of matter falling into a massive black hole.

Thanks to Chandra, astronomers now better understand black holes, which were difficult to study because of the limited capabilities of optical telescopes. While astronomers still can't see the holes themselves, they can see energetic particles that hover near their "event horizons," the outer edges of the holes.

"We know that in falling into supermassive black holes, enriched matter made from stars comes apart," says Mr. Tananbaum.

He says that masses of warped ionized iron matter is hovering around the outside of these holes. As the material gets close to the event horizon, it picks up energy making it visible. Seeing these objects, scientists have a better understanding of where black holes start.

Tananbaum says that in the past the materials photographed were much cooler and consequently much farther away from black holes - 10 to 100s of light years away. But with Chandra, the images are light-seconds and light-minutes away (a light-second is 186,282 miles).

Another explosive galaxy, Centaurus A, is also shedding light on the nature of black holes.

Astronomers believe Centaurus A collided with a small spiral galaxy several hundred million years ago. This collision is believed to have supplied gas to fuel the activity of a central black hole.

"Besides the jets, one of the first things I noticed about the image was the new population of sources in the center of the galaxy," notes Christine Jones of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "They are grouped in a sphere around the nucleus, which must be telling us something very fundamental about how the galaxy and the supermassive black hole in the center were formed."

Tananbaum is careful, however, not to overinflate the implications Chandra is raising. He says the real revelations will come after more data are analyzed in the coming months.

"The capabilities are not just theoretical," he says. "It's just a whetting of the appetite."

(c) Copyright 1999. The Christian Science Publishing Society

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