Messengers from the Extreme Universe

A unique observatory in a remote location in Argentina is starting to unravel the mysteries of High Energy Cosmic Rays.

There is no scientific consensus on the source of these particles which the shower the Earth at energies 10 million times higher than can be produced in particle accelerators! But the Pierre Auger Observatory is shedding new light on these energetic particles from space and is using them as messengers to tell us more about the wider Universe.

Scientists of the Pierre Auger Observatory held a celebration in Malargüe, Argentina, from 9 November to 11 November 2005, to mark the progress of the Observatory and the presentation of the first physics results.

To witness these extremely rare cosmic events, the observatory is constructing an array of 1600 detectors spread over 3000 square
kilometres (an area roughly the size of Cambridgeshire in the UK) in Argentina's Mendoza Province, just east of the Andes Mountains. Each of these "Cherenkov" detectors contains 3000 gallons of water and detects the electromagnetic 'shock waves' as the particles pass through. Surrounding the array is a set of 24 telescopes which, on clear moonless nights, observe the ultraviolet fluorescence light produced as cosmic ray shower particles travel through the atmosphere.

"These highest-energy cosmic rays are messengers from the extreme universe," said Nobel Prize winner Jim Cronin, of the University of Chicago, who conceived the Auger experiment together with Alan Watson of the University of Leeds. "They represent a great opportunity for discoveries."  Watson added: "How does nature create the conditions to accelerate a tiny particle to such an energy? Tracking these ultrahigh-energy particles back to their sources will answer that question."  

Commenting on the experiment's progress, Prof. Keith Mason, the Chief Executive of the UK's Particle Physics and Astronomy Research Council [PPARC], said:  "The Pierre Auger Observatory is a remarkable example of international collaboration and I am particularly proud that the UK was involved at its inception and that our scientists continue to play a key role in this project."

While a northern hemisphere site has not yet been funded, the collaboration is working to establish a northern hemisphere partner of the southern observatory, likely to be based in southeastern Colorado in the US. With observatories in both hemispheres, the Auger collaboration will have the opportunity to view the entire universe from every direction.

For more information on the Pierre Auger Cosmic Ray Observatory, visit the website. http://www.auger.org/