26 May 2011

Gamma-ray burst closest yet to Big Bang

At more than 13 billion light years away, a gamma-ray burst spotted in 2009 is the furthest – and oldest – astronomical object ever observed, a new study suggests.
Gamma ray burst

A previous record holder, a burst 12.8 billion light years distant, superceded by this new burst within 520 million years of the Big Bang. Credit: NASA/Swift/Stefan Immler

SYDNEY: At more than 13 billion light years away, a gamma-ray burst spotted in 2009 is the furthest – and oldest – astronomical object ever observed, a new study suggests.

The intensely bright explosion and its afterglow were first detected by NASA’s Swift satellite, and later confirmed by ground-based research using the Gemini Observatory, twin 8.1 metre optical-infrared telescopes in Chile and Hawaii.

“This is literally the earliest object we have ever seen in the universe and tells us that stars were beginning to form from around 500 million years after the Big Bang,” said Brian Schmidt, an astronomer from the Australian National University in Canberra and co-author of the paper to be published in the Astrophysical Journal.

“With recent advances in technology, we are now getting to a stage where we are discovering what the far reaches of the universe look like,” Schmidt said.

520 million years post-Big Bang

Prior to this record-setting find, the previous benchmark for the oldest known gamma-ray burst was 630 million years after the dawn of the universe, which is believed to have happened 13.7 billion years ago.

The source of this new explosion, known as GRB 090429B, occurred 13.2 billion years ago. This means the explosion took place only 520 million years after the Big Bang – when the universe was still in its relative infancy, less than 4% of its current age, said Schmidt, who likened the finding to a “baby picture” of the universe.

Gamma-ray bursts are incredibly luminous, high-energy events that happen when massive stars – upwards of 30 times the mass of our Sun – exhaust their nuclear fuel and collapse into themselves.

The star spews out gamma-ray photons – the most energetic form of light – and then theoretically forms a black hole. When detected in ample time, these events can shed light on the environment and conditions of distant galaxies.

Relaying signals to see explosions

These events are the largest bangs since the big one, says Schmidt, and the photons they send out are extremely rare. NASA’s Swift satellite, which launched in 2004, is designed to detect these gamma-ray photons and uses a built-in X-ray telescope to pinpoint the general origin of the burst.

Lasting for under a minute, – and was probably closer to 10 seconds at its point of origins – the burst was so bright that researchers were unable to identify its host galaxy.

“The object is so far away and the gamma-ray burst so intensely bright that the single star has outshone its entire galaxy,” Schmidt said. “It would have been about one million-trillion times brighter than our Sun, and about a million times brighter than the billion stars in the Milky Way galaxy.”

Scott Croom, an astronomer from the University of Sydney who was not involved in the research, said the most exciting thing is the distance of the burst, which could help scientists probe the early epochs of the universe.

“The challenge is that they’re very faint. The amount of information the researchers have about this [burst] is very small, so what can be inferred about the conditions at the time is quite limited – but the fact that it’s so far away is impressive in itself.”


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