Mystery blasts go back in time

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The Independent Online
Mysterious blasts of energy producing more explosive power than anything else known in the universe date back almost to the dawn of time, astronomers said yesterday. Gamma-ray bursts, first spotted in the 1960s, spew out more energy in just 10 seconds than the Sun will produce in 10 billion years.

Astronomers from the University of Cambridge have now calculated that the dimmest bursts detected are so far away that their light has taken nearly the whole of the time the universe has existed to reach us. They would have occurred at the time the first stars and galaxies were being formed, shortly after the Big Bang which created all the matter in the universe about 15 billion years ago.

The discovery also means gamma-ray bursts are about 20 times more powerful than had previously been estimated. They appear to dwarf supernovas, exploding dying stars, once thought to be the most violent objects in the universe.

Scientists still do not fully understand what causes gamma-ray bursts. It is thought they are linked with the death of massive, short-lived stars. Some experts think they occur when huge stars collapse to form black holes.