An international team of astronomers has produced the first ever picture of a supernova using gamma rays. The picture provides evidence that supernovae are one source of cosmic rays, highly energetic particles that bombard the planet, passing through us in their thousands every day.

Making an image using gamma radiation is very difficult because it is so penetrating - i.e. it passes through nearly everything. However, in this case astronomers have used Cherenkov radiation, flashes of blue light that last mere billionths of a second, to make the image.

Cherenkov radiation is caused by a charged particle exceeding the speed of light in the medium through which it travels - in this case by gamma rays interacting with the atmosphere. That doesn't mean the absolute speed of light has been exceeded, just that the gamma rays are moving so fast that they are going faster then the speed of light in the atmosphere.

Dr Paula Chadwick of the University of Durham said: "This picture really is a big step forward for gamma-ray astronomy and the supernova remnant is a fascinating object. If you had gamma-ray eyes and were in the Southern Hemisphere, you could see a large, brightly glowing ring in the sky every night."

The picture was taken using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa. The UK's involvement is funded by the Particle Physics and Astronomy Research Council, PPARC.

PPARC's Professor Ian Halliday commented: "These results provide the first unequivocal proof that supernovae are capable of producing large quantities of galactic cosmic rays - something we have long suspected, but never been able to confirm." ®

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