CAPE CANAVERAL, Fla. - The cosmos is rocked almost daily by cataclysmic explosions brighter and more massive than anything since the big bang that's thought to have given birth to the universe.
These spectacular bursts of gamma rays are found in every part of the sky and linger from a fraction of a second to a couple of minutes. The amount of energy released is almost beyond comprehension: A flash lasting several seconds contains more energy than our sun will emit during its entire 10 billion-year lifetime.
"If you added together everything else in the universe in that second, it would not be as bright as that gamma ray burst," said John Nousek, a professor of astronomy and astrophysics at Pennsylvania State University. "These might be the most distant individual objects we have ever seen."
The precise origin of these bursts remains one of astronomy's great cosmic mysteries. Scientists at NASA's Goddard Space Flight Center in Greenbelt, Md., and a team of Penn State researchers including Nousek are beginning a $250 million mission designed to help unravel the mystery.
After several delays, NASA's Swift spacecraft was scheduled to lift off aboard a Delta 2 rocket from Cape Canaveral Air Force Station as early as tomorrow afternoon.
Once in space, the 19-foot-tall spacecraft will use a trio of onboard instruments to locate and study the bursts from an orbital perch 370 miles above Earth. The nimble probe will be able to react to the explosions and point its instruments at them within 20 seconds to 75 seconds of their detection.
"The entire design of Swift was oriented around swiftness - being able to immediately detect and observe," said Anne Kinney, director of the Universe Division at NASA Headquarters in Washington. "There is no other telescope up there that has that capability."
The explosive gamma ray flashes were accidentally discovered in 1967 by a U.S. spy satellite placed in orbit to monitor the former Soviet Union for nuclear weapons tests. Two years later, perplexed scientists concluded the bursts had, indeed, come from deep space. The findings finally were declassified and published in academic journals in 1973.
Eighteen years later, NASA launched the Compton Gamma Ray Observatory, which found the explosions occurred in all parts of the sky. That meant the bursts originated far beyond our own Milky Way galaxy. The discovery gave scientists their first real hint at the enormous amounts of energy involved.
"These are the most powerful explosions in the universe," said Neil Gehrels, Swift's principal scientist at Goddard. "The amount of energy in these explosions is so large that if there was a gamma ray burst that occurred within our neighborhood in the Milky Way - let's say the one-tenth of the Milky Way nearest to our solar system - the gamma ray radiation would actually strip the atmosphere off of the Earth."
An Italian astronomy satellite discovered in 1997 that the gamma ray bursts often leave a faint afterglow that sometimes persists for weeks. Swift will survey the cosmos for the bursts and their afterglow during a mission scheduled to last at least two years. During that time, program scientists expect to observe more than 200 explosions.
The spacecraft is equipped with three instruments. One will detect the bursts and find the general location within a matter of seconds. Two others will pinpoint the origin and study the explosions' afterglow in ultraviolet, X-ray and optical light.
Swift's research team, which includes British and Italian scientists, hopes the findings will help answer a basic question about the flashes: Where do they come from?
A leading theory is that the bursts represent the death knell of giant stars as their cores' collapse into stellar black holes so massive that even light can't escape from the objects' gravitational pulls. The dying stars' outer layers explode in giant supernovas. Other bursts may be the result of collisions between black holes or super-massive neutron stars - objects so dense that every person on Earth would fit into a space the size of a sugar cube.
"We never know which direction these messages are going to come from, but we know they will be brief - more like postcards than letters," Kinney said. "The Swift mission is going to give us unprecedented ability to decode these messages."
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