UK astronomers have helped discover the most distant object known in the universe – an overweight star that destroyed itself in an explosion of unimaginable force.
Dubbed GRB 090423, the blast was detected by a NASA satellite in space called Swift on April 23. It set off alarms and, within minutes, members of the Swift team at Leicester University and colleagues at the US’s Harvard-Smithsonian Centre for Astrophysics were monitoring the discovery.
Their observations show that the incredible explosion occurred when the universe was only 630 million years old – only a twentieth of its current age. Astronomers speculate that such huge blasts may be caused by the collapse of a massive star to form a black hole.
Swift detected the blast as a ten-second long outburst, followed by an afterglow visible in X-ray light.
Within three hours, Professor Nial Tanvir, of Leicester University, and his colleagues detected a source for the blast using the heat-seeking UK Infrared Telescope on Mauna Kea, Hawaii. “Burst afterglows provide us with the most information about the exploded star and its environs,” said Professor Tanvir. “But because afterglows fade out so fast, we must target them quickly.”
At the same time, the Harvard team were using another instrument on Hawaii, the Gemini North Telescope, which has previously discovered planets, to take infrared images and measure the blast’s distance. Their results showed it was about 13 billion light-years away.
Professor Edo Berger, of Harvard University, said yesterday (Tue): “I have been chasing gamma-ray bursts for a decade, trying to find such a spectacular event. We now have the first direct proof that the young universe was teeming with exploding stars and newly-born black holes only a few hundred million years after the Big Bang.”
As word spread about the record distance, additional telescopes around the world were turned towards GRB 090423 to observe the afterglow before it faded away. They confirmed the burst’s redshift to be 8.2 – the highest ever measured. It corresponds to a distance of 13.035 billion light-years.
The previous record holder was a burst seen in September 2008. That was 190 million light-years closer to us than GRB 090423. Swift has discovered a previous record-holder that is much closer to home.
Picture: The record-breaking gamma-ray burst imaged by the Gemini North Telescope. (Photo: Gemini Observatory/NSF/AURA, D. Fox and A. Cucchiara (Penn State Univ.) and E. Berger (Harvard Univ.)
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