The burst's afterglow seen at lower energy X-ray wavelengths
Astronomers have recorded the most powerful radiation blast from deep space yet detected.
The event was observed by Nasa's recently launched Fermi Gamma-ray Space Telescope and reported in the online edition of the journal Science.
The source of the blast is assumed to be the catastrophic implosion of a star, to create a black hole.
Scientists say the spectacle's energy release was equivalent to thousands of ordinary exploding stars.
"This is the most spectacular burst ever seen at high energy," said Dr Valerie Connaughton, a scientist from the University of Alabama, Huntsville, and a member of Fermi's Gamma-ray Burst Monitor (GBM) instrument team.
THE FERMI MISSION
Spacecraft was launched in June 2008 on a five-year mission
It is looking at the Universe in the highest-energy form of light
Fermi is 2.8m (9.2ft) high and 2.4m (8.2ft) in diameter
The spacecraft orbits at an altitude of 565km (350 miles)
It could pick up about 200 cosmic explosions each year
"If the event that caused this blew out in every direction instead of being a focused beam, it would be equivalent to 4.9 times the mass of the Sun being converted to gamma rays in a matter of minutes."
Theory suggests that a certain type of giant, short-lived star can experience catastrophic collapse when the nuclear reactions at its core can no longer support its mass.
When this sort of star implodes, to create a black hole, it generates jets of material that punch their way out of the collapsing mass at near light-speed, to produce extremely high-energy emissions of light.
Most of these emissions last only a few seconds, however. The one seen by Fermi at 0013 GMT on 16 September last year, in the constellation Carina, went on for 23 minutes.
Researchers working on the Nasa mission say the extraordinary longevity of the gamma-ray burst may force them to change their theories about how these colossal blasts work.
Impression: The collapse event produces super-fast jets of particles
"We were waiting for this one," said Peter Michelson, the principal investigator on Fermi's Large Area Telescope at Stanford University.
"Burst emissions at these energies are still poorly understood, and Fermi is giving us the tools to understand them."
The explosion has been designated GRB 080916C. Analysis of the light suggests its point of origin is about 12 billion light-years from Earth (Seen from Earth, it came from just below the star Chi Carinae in the southern sky).