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Science File

Shaking Up Black Hole Theory

September 06, 2003|K.C. Cole | Times Staff Writer

For all their pull on the imagination, black holes have always seemed somewhat sedate -- passive one-way portals that swallow light and anything else that come within gravitational grabbing distance.

But recent observations by a group of UCLA astronomers of the black hole at the center of the Milky Way have found that the path to oblivion is surprisingly churned up -- more like a tornado than a funnel.

Such close-up views of matter swirling around the mouth of the black hole weren't possible until recent improvements to the Keck telescopes in Hawaii allowed observations in previously obscured bands of infrared.

Radio signals have long suggested calm conditions. Recent X-ray images have caught energetic flare-ups, but only about once a day.

In the infrared, however, the hole -- 26,000 light-years from Earth -- is a constantly (if irregularly) flickering beacon.

It's like seeing the black hole's heartbeat, said UCLA astronomer Andrea Ghez. "Is it calm? Is it nervous? It turns out it's a lot more excited than we thought."

The situation, she said, is probably analogous to that on the sun: layers of electrically charged gas orbiting at different speeds, sheering against each other, tangling up magnetic fields.

"From a distance, the sun looks calm," Ghez said. "But when you look in detail, you can see that it's very turbulent."

The throat of the hole is even more tumultuous, with superheated molecules slamming into each other, causing shocks. Understanding these conditions in detail will help astronomers discover why our black hole is so unusually black. Those in other galaxies emit far more light, while ours seems to keep its vast energy close to home. "How does it hide all that energy?" Ghez asked.

The answers are swirling around in all that gas.

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