Page last updated at 23:44 GMT, Friday, 19 September 2008 00:44 UK

Observatory detects record burst

GRB 080913 (Nasa)
GRB 080913 seen by Swift's X-ray and UV/optical sensors

The Swift space telescope has detected a gamma-ray burst some 12.8 billion light-years from Earth - a record.

These intensely bright but fleeting flashes of very high-energy radiation signal some of the Universe's most violent happenings.

This blast, designated GRB 080913, probably originated in the catastrophic explosion of a massive star.

"This is the most amazing burst Swift has seen," said lead scientist Dr Neil Gehrels.

"It's coming to us from near the edge of the visible Universe," explained the researcher from the US space agency's (Nasa) Goddard Space Flight Center.

The burst was detected at 0547 GMT on 13 September, in the constellation Eridanus.

Because light moves at finite speed, looking farther into the Universe means looking back in time. The distance this flash has had to travel means Swift is seeing the event less than 825 million years after the Universe came into being; and some 70 million years further back in time than the previous record holder, a burst detected in 2005.

Indeed, it is one of the most distant objects ever seen. Only the light from some faint galaxies has been detected beyond this burst - 100-300 million light-years further away.

Scientists are very keen to probe these great distances because they will learn how the early Universe evolved, and that will help them explain why the cosmos looks like it does now.

Swift was launched in 2004. It is a three-in-one observatory. Its Burst Alert Telescope is set up to catch the intense but fleeting flash of very high-energy gamma radiation that initially signals a GRB event. Swift then swings itself to look directly into the flash with X-ray and ultraviolet/visible telescopes.

This longer wavelength afterglow can last days and Swift alerts ground-based observatories to join the spectacle.

Indeed, it is the ground campaign that establishes the distance.

In this case, astronomers using the European Southern Observatory's 2.2m telescope at La Silla and Very Large Telescope at Paranal (both in Chile) targeted the afterglow.

Analysis of the light spectrum confirmed the blast had a redshift of 6.7. Redshift is a measure of the degree to which light has been "stretched" by the expansion of the Universe. The greater the redshift, the more distant the object and the earlier it is being seen in cosmic history.

The figure 6.7 equates to 12.8 billion light-years.

Although a Nasa-managed mission, Swift has significant British and Italian contributions.

The UK's major input has been to provide an X-ray camera and elements of the UltraViolet/Optical Telescope.

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