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Extending the edge of the observable Universe
Posted: 26 May 2011

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After two years of analysing images and data from gamma-ray burst (GRB) 090429B, astronomers estimate that its light began travelling on its journey just 520 million years after the Universe began.

GRBs are the brief burst of high-energy radiation that mark the death of massive stars. Over time this emissions fades to an afterglow of light at other wavelengths. Initially discovered by the Swift satellite, the subsequent afterglow was detected by the Gemini North telescope at infrared wavelengths.

Data collected by the Gemini North Observatory of the afterglow at infrared wavelengths helped astronomers to determine the distance of the GRB. Image: Gemini Observatory / AURA / Levan, Tanvir, Cucchiara. .

Although early indications suggested the GRB was a potential distance record holder, the team needed more information to confirm this. Using data from Gemini and combining it with images from the United Kingdom Infrared Telescope, which also sits on Hawaii’s Mauna Kea, the team was able to estimate the redshift – a term used to quantify an object's distance – of GRB 090429B to 9.4, the equivalent of 13.14 billion light years away. The previous record-holder, located at a redshift of 8.2, a little over 13 billion light years away, was detected just one week previously (see our previous news stories here and here for more).

“The fact that we were never able to detect anything in the spot where we saw the afterglow in the Gemini data gave us the missing link in converging on this extremely high redshift estimate,” says team leader Antonino Cucchiara. “We looked with Gemini, the Hubble Space Telescope and also with the Very Large Telescope in Chile and never saw anything once the afterglow faded. This means that this GRB’s host galaxy is so distant that it couldn’t be seen with any existing telescopes. Because of this, and the information provided by the Swift satellite, our confidence is extremely high that this event happened very, very early in the history of our Universe.”

The blast from this dying star may have occurred just 520 million years after the big bang. Image: NASA / Swift / Stefan Immler.

Cucchiara cautions that, like any other finding, there are inevitable uncertainties. “However, if I were in Vegas, I would never bet against the odds that this is the most distant GRB ever seen and we estimate that there is even a 23% chance that it is the most distant object ever observed in the Universe,” he adds.

The team say that the behaviour of GRB 090429B is in line with other "normal" GRB events, suggesting that there were many generations of stars before it, an implication that itself says that the extremely young Universe was already a very busy star factory.

The finding was announced at the American Astronomical Society meeting held in Boston, Massachusetts this week, and will be reported in The Astrophysical Journal.