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Thursday, 19 February 2009

A team of UWA astrophysicists has captured one hour of valuable video footage of the aftermath of a massive gamma ray explosion 11 billion years ago – just a few billion years after the Big Bang. In the January 2009 edition of ScienceNetwork WA , Carmelo Amalfi , discusses how this ancient light was detected for the first time on Earth by a one-metre robotic telescope installed just last year at the Gingin gravitational wave observatory, 70 km north of Perth.

The Zadko Telescope near Gingin was the first to observe light from an 11-billion-year-old gamma ray explosion. The UWA researchers’ announcement coincides with the International Year of Astronomy in 2009 and marks the discovery of one of the most distant explosions observed from Australia. The team focused on the faint flare-up after it was initially detected and its coordinates relayed to ground stations by the US Swift satellite, launched in 2004 to monitor gamma ray bursts.

The Zadko telescope near Gingin recorded the explosion two hours after Swift detected it, with the more advanced optical telescopes in Chile unable to observe the event until nine hours later.

“We have a very expensive CCD camera used in imaging the optical afterglow of a gamma ray burst, and that actually failed on the night,” said UWA research fellow Dr David Coward.

“Luckily, we had a video camera about the size of a cigarette packet that we managed to connect to the back of the telescope, and just pressed ‘play’.

“We did that for about an hour – recording this 11-billion-year-old light reaching us from the distant explosion.”

These explosions are extremely bright flashes of gamma radiation, regarded as the most powerful in the universe since the Big Bang. Had it gone off in our galaxy, gamma radiation could have potentially affected life on our planet, and many scientists believe it has done so in Earth’s past.

NASA satellites have been observing gamma ray bursts since the 1970s, recording them at a rate of about one a day. These satellites were looking for gamma rays emitted by Soviet nuclear tests but instead found flashes of gamma ray bursts arriving from different parts of the sky.

The UWA School of Physics team consists of UWA PhD student Eric Howell and academics Dr Ron Burman and Professor David Blair. Results of their work are published in the journal Astrophysical Journal Letters.

Dr Coward said it was important to know where and how often gamma ray bursts occurred because their effects could be devastating on Earth. The light they emit can outshine the galaxy they occupy. Burning bright for a few seconds to several minutes, they are billions of times brighter than the sun, making them briefly the brightest source of radiation in the universe.

“The stars that cause gamma ray bursts are about 100 times more massive than our sun,” he said.

The researchers have developed a computer program, the Probability Event Horizon filter, which analyses NASA data to predict such events (reported by ScienceNetwork WA, September 2007).

Some of these flashes are associated with powerful supernovae, or collapsing stars – the explosions marking the death of massive stars and their rebirth as black holes.

Media references

Dr David Coward , (+61 8) 6488 4563

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