A recent gamma-ray burst was the biggest explosion ever seen, second only to the "big bang" that gave birth to the universe, astronomers 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.
It 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.
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. Only the fading afterglow could be detected in the past.
But thanks to a system set up by NASA and European scientists, on the morning of January 23 orbiting detectors caught the burst. Within seconds a computer was signaled 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 extraordinarily 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," said Galen Gisler, an astrophysicist at Los Alamos National Laboratory in New Mexico.
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, and colleagues looked at the "redshift" of the star-which tells how much the light has faded and changed as it traveled trillions of miles 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 a second, or a total of about 5.9 trillion miles. This shocked 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."