Tuesday, May 26, 2009

The Mystery of Black Holes:Astrophysicists Discover New Details of How Stars Collapse

Black holes have baffled astronomers for decades. The first one was discovered in 1975. Now for the first time scientists are watching them unfold before their very eyes.

As a child, Peter Brown, an astronomy and astrophysics graduate student at Pennsylvania State University in Philadelphia, was fascinated by outer space. "Looking at Halley's comet thru the telescope when I was, when I was younger had a definite impact on me," he says.

As an adult, however, comets weren't enough for Brown. He wanted to see bigger, brighter things. Now for the first time he's able to see massive newborn black holes. "What fascinates me is that things that we're observing are so far away," he says.

Working with astrophysicists, Brown is part of a satellite project called Swift. Swift snaps photos of baby black holes being born, revealing a messier birth than previously thought. Dave Burrows, an astrophysicist at Pennsylvania State University, says, "So instead of these things sort of being a one instantaneous event, they seem to go on for hundreds of seconds as the black hole kind of gobbles up material."

Researchers now believe after a star dies and collapses, forming a black hole, the black hole continues to cause havoc, devouring material while at the same time spewing it back out in a series of multiple outbursts of light.

"What we're seeing is a lot of interesting things happening in the first few minutes after the explosion that we could never really see before," Burrows says. Catching new glimpses of black holes helps scientists better understand how the universe formed and puts curious minds at ease.

"Black holes are inherently fascinating because they are sort of mind-bending concepts," Burrows says. Concepts that stargazers like Brown to learn more about.

The Swift satellite, used to catch black holes in action, is unique because it detects a light burst from a dying star and rotates within minutes to record the explosion. Swift received a "best of what's new" award from Popular Science magazine.

BACKGROUND: Astronomers have always thought that large stars die in one big explosion that creates a black hole. New data from NASA's Swift satellite indicates that a star dies through a series of explosions -- three or four of them -- before forming a black hole.

WHAT IS SWIFT: Swift was launched in November 2004 to collect and analyze data on gamma ray bursts and other higher-energy happenings in the universe. Using Swift's state-of-the-art X-ray and ultraviolet telescopes, astronomers can now see gamma ray bursts within minutes, instead of hours or days, and can thus catch a glimpse of newborn black holes.

WHAT THEY FOUND: Whenever a massive star explodes, first there is a blast of gamma rays, followed by intense pulses, or "hiccups," of X-rays. There have been hints of such activity before, but Swift has detected more than a dozen clear cases of multiple explosions. Scientists are now exploring several hypotheses to describe this new phenomenon.

ABOUT BLACK HOLES: A black hole forms when a massive star has used up all its fuel and explodes, becoming a supernova or its more powerful cousin, a hypernova. The reason the Sun and other stars emit light is because trillions of nuclear reactions are taking place at the cores. With core temperatures of millions of degrees, hydrogen atoms can convert into helium atoms, emitting radiation in the process. At some point, however, all the atoms are used up and no more nuclear fusion can take place. Without that outward counter-force to the pull of gravity, a star collapses inward, eventually reaching a point where the attractive gravitational force is so strong, not even light can escape.

The American Astronomical Society contributed to the information contained in the TV portion of this report.

Source:Science Daily,December 1,2005

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