Mon, Nov 22, 2004 - Page 7 News List

Space observatory sent to chase black holes

SPACE RESEARCH The `Swift' spacecraft will scan space and gather data on gamma ray bursts, which are thought to indicate the birth of black holes


The fastest-swiveling space science observatory ever built rocketed into orbit Saturday to scan the universe for violent celestial explosions that astronomers believe represent the birth screams of black holes.

NASA launched the observatory -- named Swift for its speedy pivoting and pointing -- following weeks of delays caused by hurricanes and a three-day postponement due to rocket trouble. The unmanned rocket climbed smoothly through a cloud-flecked midday sky, and delighted flight controllers wished the spacecraft a successful mission.

Swift, a US$250 million collaboration by NASA, Italy and Britain, should begin its hunt for gamma ray bursts by January and erase some of the mystery surrounding these explosions and black holes.

Gamma ray bursts are the most powerful events in the universe, exceeded only by the cosmic curtain-raising Big Bang itself. Lasting just a few seconds on average, the bursts appear out of nowhere like flashlight beams and are thought to signal the formation of black holes.

Astronomers theorize the collapse or collision of massive stars is what produces black holes -- so dense not even light can escape -- and that the resulting gravitational energy sends gamma rays shooting out across time and space.

"We think that, perhaps, bursts are the birth cries of black holes and we're seeing these throughout the universe," said NASA's Neil Gehrels, principal scientist.

A single gamma ray burst releases more energy than the sun will emit in its entire lifetime at all wavelengths, Gehrels said.

Put another mind-blowing way, "If you added together everything in the rest of the universe during that second, it would not be as bright as the gamma ray burst," said Pennsylvania State University astrophysicist John Nousek, director of mission operations.

So far, astronomers have managed to identify only a couple dozen gamma ray bursts, as close as a few million light years and as far as 12 billion light years. Swift should zero in on two gamma ray bursts a week as far away as 15 billion light years, representing the very first generation of stars, for a grand total of more than 200 during the planned two-year mission.

The spacecraft will scan one-sixth of the sky at any one time and thus see one-sixth of all gamma ray bursts out there. The observations will help scientists learn more about what the bursts are, how black holes are formed and how many are out there.

As soon as Swift's gamma ray burst-alert instrument spots an explosion, the spacecraft will quickly turn all by itself so that two other on-board telescopes can observe the X-rays and ultraviolet and optical light streaming from the afterglow.

This swinging into position will take just a minute, lightning speed by astronomical standards because of Swift's six momentum wheels, double the usual number for a science satellite. Speed is crucial because once the ever-so-brief gamma ray burst subsides, the afterglow is difficult to find and fades within hours or sometimes weeks.

News of the gamma ray burst and its precise location instantly will be relayed to astronomers everywhere by the mission control center at Penn State. Ground observatories can then be aimed to assist in the afterglow analysis.

Deputy project manager Tim Gehringer calls Swift "the roadrunner of spacecraft, speeding from birth to birth as it advances mankind's knowledge of the most violent explosions in the universe."

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