A satellite sent aloft to scan space for gamma rays alerted astronomers last week to a burst of radiation from a point 12.8 billion light years away, allowing telescopes atop Mauna Kea to record the most distant cosmic explosion ever seen.

Lennox Cowie, astronomer with the University of Hawai'i's Institute for Astronomy, yesterday said the explosion was probably caused by the collapse of a massive star, an event that released about as much energy as the sun will emit over its 10 billion-year life span.

The remnants of such explosions fade away in days, so scientists set up an automated communication network to alert them when the Swift Gamma-Ray Burst satellite, launched last year, detected radiation so they could immediately train the world's most advanced telescopes on the source.

In Hawai'i, the call came in at 2 a.m. Sept. 4 to UH astronomer Paul Price, who then took charge of aiming NASA's Infrared Telescope Facility on Mauna Kea and the MAGNUM telescope on Haleakala at the source of the explosion.

Nobuyaki Kawai of the Tokyo Institute of Technology led a team that used the 27-foot Subaru Telescope on Mauna Kea to measure a precise distance to the explosion, according to a news release.

Astronomers so far have identified only 50 other objects at such a great distance from Earth.

Gamma ray bursts last just a few seconds on average, but are the most powerful cosmic events, short of the "big bang" that is believed to have created the universe. The bursts are thought to signal the formation of black holes.

"Because these explosions are so bright, they give us the opportunity to study stellar birth and death in the most distant universe in a manner we could only dream about a couple of years ago," Price said.

Astronomers usually study the early universe by observing the light from distant galaxies, or light generated by quasars, which are believed to be black holes that are consuming cosmic dust.

The gamma ray bursts are brighter than both and can be seen across the known universe, so the study of the bursts may soon allow astronomers to observe objects more distant than any yet detected.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.