Scientists find black hole's 'point of no return'

70652986 — Mon, 26 Mar 2007 06:23:58 -0400

By a score of 135 to zero, scientists using NASA's Rossi X-ray Timing Explorer have compared suspected neutron stars and black holes and found that the black holes behaved as if each one has an event horizon, the theoretical border from beyond which nothing, not even light, can escape.

The team found that X-ray light emitted from these two types of regions behaved differently. As expected, the neutron stars appeared to have a hard surface, which erupts in an X-ray explosion every several hours. The black holes appeared to have no surface. Matter falling toward the black hole seems to disappear into the void.

Ron Remillard of the MIT Kavli Institute in Cambridge, Mass., led the analysis and discussed his team's result Jan. 9, 2006, at a press conference at the 207th meeting of the American Astronomical Society in Washington. His colleagues are Dacheng Lin of MIT, and Randall Cooper and Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics in Cambridge.

"Event horizons are invisible by definition, so it seems impossible to prove their existence," said Remillard. "Yet by looking at objects that pull in gas, we can infer whether that gas crashes and accumulates onto a hard surface or just quietly vanishes. For the group of suspected black holes we studied, there is a complete absence of surface explosions called X-ray bursts. The gas that would fuel such bursts appears to vanish."

Uncovering new evidence for 'event horizons' surrounding black holes

70652986 — Mon, 26 Mar 2007 05:04:29 -0400

With results that fundamentally differ from earlier black hole studies, Harvard researchers have shown that some recently discovered black holes are not only ultra-dense, but actually possess event horizons that "vacuum up" energy from their surroundings. "Watching matter flowing into a black hole is like sitting upstream of a waterfall and watching the water seemingly vanish over the edge," said Ramesh Narayan, chairman of the Harvard Astronomy Department. The astronomers used NASA's Chandra X-Ray Observatory to study some of the darkest black holes yet observed. They strongly confirmed the reality of the "event horizon," the one-way membrane around black holes predicted by Einstein's theory of relativity.

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Scientists find black hole's 'point of no return'

Uncovering new evidence for 'event horizons' surrounding black holes