Mighty explosion caught by amateurs

Mark Armstrong: "It's great to see one at last."

By Dr David Whitehouse BBC News Online science editor

British amateur astronomers have detected, for the first time from the UK, the faint fading glow of a titanic explosion almost at the edge of the observable Universe.

They detected the decaying light in the same position in the sky from where just a few hours earlier a burst of high-energy radiation - gamma-rays - was recorded.

The initial gamma ray burst (GRB) was detected at 1206 GMT on 4 October, by detectors onboard the High Energy Transient Explorer (Hete) satellite.

Within seconds, an automatic alert was generated and e-mailed to observers worldwide.

Several large telescopes automatically interrupted their planned observations and swung towards the position of the explosion to see what they could find.

The first detection of a fading point of light in the same position was by Derek Fox at the Mt Palomar Observatory in California, US, just nine minutes after the initial alert. But later that day, British amateurs also saw the object - a first for them.

Telescope race

Fading afterglows of GRBs have been seen only a few times before. Astronomers believe that by analysing the afterglow, they may solve the mystery of the GRBs.

They are bursts of energy that occur far away in the Universe. Astronomers cannot adequately explain them, as they must be the most energetic events in the Cosmos since the Big Bang itself.

The fading afterglow
(Image by Martin Mobberley

Black hole collisions have been suggested.

In recent years, some astronomers have begun to believe that they are not so energetic but only appear so intense because the light of the explosion is amplified and beamed in our direction, giving us an exaggerated estimate of the energies involved.

Getting to the bottom of this considerable mystery represents a challenge to professional astronomers - and now amateurs have shown they are up to the task as well.

As soon as a GRB is detected, a race begins with observers around the world trying to pinpoint its exact location because the radiation fades from view after only just a few hours.

Ancient light

Following the detection of the afterglow from California, Dr Nial Tanvir, a researcher in GRBs at the University of Hertfordshire, alerted the UK network of astronomers during the afternoon of 4 October, while arranging for the burst to be observed by several of the UK's large overseas telescopes.

Shortly afterwards, amateur astronomers around the UK trained their telescopes towards the position of the fading object.

Martin Mobberley and telescope: Part of the alert network

The first successful detection was from Mark Armstrong in Kent, a veteran and highly successful searcher for explosions in deep space.

"We've been chasing GRBs for a couple of years now, and it's great to see one at last," he told BBC News Online.

Nick James in Essex saw it soon afterwards. "The amazing thing is that the light we're detecting began its journey before the Solar System was even formed," he said.

They were closely followed by Tom Boles and Martin Mobberley in Suffolk, David Strange in Dorset, Peter Birtwhistle in Surrey, Eddie Guscott also in Essex and observers at the University of Hertfordshire Observatory.

Last moments

Dr Nial Tanvir added: "By putting together data from telescopes all around the world, we can learn more about what causes GRBs, which at the moment are still a mystery.

"The favourite idea is that they are violent ejections produced during the last moments in the life of some massive stars, just as they are in the process of collapsing to form black holes. Because they are unpredictable and fade so fast, when they do occur we try to observe them with every telescope we can."

The US space agency (Nasa) takes the role of amateur astronomers in GRB research sufficiently seriously that it helps fund the liaison between the American Association of Variable Star Observers and other amateur groups worldwide.

In the UK, the co-ordination effort is led by Guy Hurst of The Astronomer magazine.