'Live' Gamma Burst Was Huge, Astronomers Say

WASHINGTON (Reuters) - The first gamma-ray burst that astronomers got to watch ``live'' was the biggest explosion ever seen, second only to the ``big bang'' that gave birth to the universe, they said Thursday.

The burst of energy, caught on camera with the help of a complex link of satellites, telescopes and e-mail, came from the far reaches of the universe, sending light, X-rays and radio waves two-thirds of the way across the universe.

But it probably looked so intense because it came as a beam of energy, rather than in an explosion in all directions, the international team of astronomers said in a series of reports.

Nonetheless, the explosion -- probably caused by the birth of a black hole, or by the collision of two massive stars known as neutron stars -- was so enormously powerful that it projected its energy across nine billion years worth of time and space.

Gamma ray bursts have long mystified astronomers. First seen by accident in the late 1960s by U.S. scientists looking for Soviet nuclear weapons tests in space, they come without warning and only the fading afterglow could be detected.

But thanks to a system set up by NASA and European scientists working with teams at various universities, on the morning of January 23 orbiting detectors caught the burst and within seconds signaled a computer that in turn woke up an observatory in New Mexico and caught the explosion on film.

``It's like the difference between watching two cars collide and coming on the accident scene several hours later,'' said physics professor Carl Akerlof of the University of Michigan.

What they saw was bright.

``If you had been gazing at that spot with binoculars, you would have seen a 'star' appear, brighten, and fade within minutes, an unbelievably violent event from the very edge of our universe,'' Galen Gisler, an astrophysicist at Los Alamos National Laboratory in New Mexico, said in a statement.

In a series of papers published in the journals Nature and Science, the teams of scientists described what they saw.

Shrinivas Kulkarni, an astronomer at the California Institute of Technology (Caltech), and colleagues looked at the ''redshift'' of the star -- which tells how much the light has been faded and changed as it traveled trillions of miles (km) to reach the Earth.

The redshift is 1.6, which means the burst was very far away and thus extremely powerful.

``It is 70 percent of the age of the universe,'' Kulkarni said. ``So if you think the universe is 12 billion years old, this is about nine billion years old.''

That also makes it nine billion light years away -- a light year being equal to the distance light travels in one year at a speed of 189,000 miles (300,000 km) a second, or a total of about 5.9 trillion miles (9.5 trillion km).

This alarmed astronomers. ``The object would be so bright that for (the) 100 seconds it was on, it outshone the whole universe, which to me is an amazing concept,'' Kulkarni said.

``We were stunned,'' Caltech's George Djorgovski added in a statement. ``This was much further than we expected.''

But the idea is not so alarming if the energy was concentrated in a beam, like a laser. And other teams found evidence of this.

Alberto Castro-Tirado of the Laboratorio de Astrofisica Espacial y Fisica Fundamental in Madrid, Spain and an international team of colleagues found the light faded in a way that did not look like a fireball-type burst.

Jens Hjorth and colleagues at the University of Copenhagen in Denmark found that the light from the burst, dubbed GRB 990123, was hardly polarized at all -- surprising if it had passed through the magnetic field created by a fireball but not surprising if it came in a beam.

In turn, this fits in with the idea of a super massive star collapsing on itself to form a black hole, Kulkarni said.

``We think that when very massive stars die, they form a black hole and when the debris rains in on the black hole, you get a gamma-ray burst,'' he said.

``It's not an unreasonable assumption,'' Akerlof said in a separate interview. But it could be something else.

``The first thing that came to mind when it was obviously cosmological is that this would be a binary pair of neutron stars that would spiral into each other,'' he added.

``If you have something spinning, it is easier for it to go out from the axis of spin than from the sides.''

The only way to know more, he said, will be to look for more gamma-ray bursts and study them.

 

'Meltdown' Sparks War Of Words Over Three Mile Island

MIDDLETOWN, Pa. (Reuters) - Nearly 20 years after the worst U.S. commercial nuclear accident, members of the public are still trying to get the powers-that-be to admit that what happened at Three Mile Island was a meltdown.

Thursday, just three days before the 20th anniversary of the disaster, Pennsylvania will unveil the official historical marker for the site along the Susquehanna River just south of Harrisburg, where two of the four 350-foot cooling towers that once symbolized a nuclear nightmare continue to belch steam into the atmosphere.

A committee made up mainly of politicians, bureaucrats and utility executives avoided ``the m-word'' in a message that will appear in gold lettering on a dark blue metal scroll. Instead, the Pennsylvania Historical and Museum Commission marker will tell posterity that ``part of the nuclear core was damaged.''

``It should say that a partial meltdown occurred, but this was the best I could get,'' said Eric Epstein of the group Three Mile Island Alert, the committee's lone environmentalist.

``The original was even worse. They wanted to say that a major disaster was averted. No, it was a major disaster.''

Yet the word ``disaster'' also is absent from the marker's 64-word synopsis of the accident that changed the face of nuclear power and made the oafish cartoon character Homer Simpson a parody of nuclear plant operations.

At about 4 a.m. on March 28, 1979, sirens pierced the darkness around Three Mile Island's Unit-2 reactor when a relief valve stuck, releasing radioactive water as steam. Plant operators then mistakenly shut off cooling water for the 150-ton radioactive core, prompting a partial meltdown and the evacuation of about 140,000 people from the Harrisburg area.

Half the core melted and 20 tons of molten material ran to the bottom of the reactor where the remaining water held it in check. The plant spewed radioactive gas into the air for days.

TMI spokesman Ralph DeSantis says there is a very good reason why damage is a better descriptive word than meltdown.

``It's more accurate,'' he said. ``Some of the fuel did melt. But the damage to the reactor wasn't just from melting. Very hot fuel that had not melted shattered like glass when water was reintroduced to the reactor. And other components, like fuel rods, were damaged. It was all inter-mixed.''

Critics say the utility and the state want to avoid the word meltdown because it conjures images of the deadly 1986 explosion at the Soviet Chernobyl plant, at a time when the U.S. nuclear power industry is entering a new era of utility deregulation.

But the war of words means little to people like Debbie Baker, who lived 5-1/2 miles from the plant at the time of the disaster. Her son Bradley, now 19, was born nine months later with Down's syndrome. Her doctor blamed radiation and she became one of only a handful of local residents to reach settlements with Morristown, N.J.-based plant owner GPU Inc. (NYSE:GPU - news)

``What I want, is to know for certain. My doctor may say he firmly believes that radiation was the cause of my son's disability. But I want the 100-percent answer. That's what is frustrating to me,'' she said.

More than 2,000 lawsuits that followed her settlement were dismissed for lack of evidence by a U.S. judge in 1996, after government studies showed no evidence of accident-related health effects, other than mental and emotional stress. The dismissal ruling has been appealed.

Meanwhile, Baker said the debate over the historical marker is only the latest example of how local residents are ignored. The most glaring was in 1985, when the U.S. Nuclear Regulatory Commission allowed GPU to restart the undamaged TMI Unit-1 reactor, even though Dauphin County residents had voted 2-to-1 against the move in a nonbinding referendum.

``People don't have a vote on what goes into their neighborhoods. Democracy really isn't alive here,'' said Harrisburg activist Gene Stilp, whose No Nukes Pennsylvania group will place their own historical marker at Three Mile Island during an anniversary ceremony set for next Sunday.

Their marker blames a ``nuclear meltdown'' in part on ''corporate criminal acts,'' recalling the fact that a GPU subsidiary pleaded guilty and no-contest to criminal charges that Three Mile Island safety records were falsified just before the accident.

Meanwhile, Three Mile Island is expected to make history again this summer. After a $1 billion 14-year cleanup, TMI-2 will never reopen. But TMI-1 will be sold for $100 million to AmerGen Energy Co., a joint venture of PECO Energy Co (NYSE:PE - news) . and British Energy, in the first-ever sale of a nuclear plant.