OSB archive
OSB archive

Neutrinos in the deep freeze

Pete Wilton

Tiny flashes of blue light from beneath the icy South Pole could help scientists uncover the origins of cosmic rays and neutrinos.

These flashes occur when neutrinos created by cosmic rays strike nuclei in the ice, releasing energetic muons which travel through the ice faster even than light can -  producing a burst of Cherenkov radiation. This is detected by IceCube, a 'telescope' made up of thousands of optical sensors buried up to 2.5km deep in the Antarctic icecap. This location is ideal because under the huge pressure at such depths the ice is free of air bubbles and very clear.

Subir Sarkar of Oxford University's Department of Physics leads the British involvement in IceCube, he told The Telegraph's Richard Gray: 'Cosmic rays were discovered 100 years ago, but we still have no idea where they come from. At first glance, IceCube seems like a crazy experiment. How can you study the sky when you bury your detectors a mile beneath the ice? But it gives us a new way of tracing their paths back to their source.'

'The real excitement is that neutrinos and cosmic rays will reveal an entirely new way of looking at the universe and allow us to see into places where we haven't been able to before.'

'Currently we have no way of peering into black holes through the dust and gas that surrounds them, so if high energy neutrinos are being emitted from their fringes, then we can 'see' into places we haven't been able to before.'

IceCube isn't due to be completed until 2011, when all the optical sensors will have been installed, but as early as 2006 its detectors began to pick up the flashes of neutrino collisions. It's already identified an area of the sky near the constellation of Vela as a prolific source of cosmic rays.

Being able to spot these very rare neutrino collisions could help us understand the nature of the dark matter thought to make up around 23% of our Universe.