Is the active galaxy M87 in our local cluster a
source of ultra-high energy cosmic rays?
A photomultiplier camera of one of the
Ultrahigh Energy Cosmic Rays
Cosmic rays are relativistic charged particles, such as protons or Helium nuclei, hitting Earth from outer space. The highest energy cosmic ray ever measured had an energy of 3x1020 eV. So far it is a big mystery where these particles come from and how they acquire their energies. It is difficult to imagine how even the most powerful celestial objects can accelerate ordinary particles to such energies. Also these particles will quickly loose their energy on their travel through space. This suggests an origin rather close to Earth. The highest energy events seem to originate from random locations at the sky and cannot be correlated to any known object in the universe. The flux of the highest energy cosmic rays is only about 1 particle per km2 and century. Therefore huge detectors are needed to measure sufficient numbers of events in the limited lifetime of an experiment. With the Pierre Auger Experiment, consisting of a 3000 km2 detector array and 34 fluorescence telescope in Argentina, we try to measure cosmic rays at highest energies to resolve the mystery of their origin.
At present (Jan 2006) 919 water Cherenkov detectors and 18 fluorescence telescopes (of 24) are operational. The first results were reported in July 2005.
The Schools of Physics and Astronomy and Electrical Engineering of the University of Leeds are key players in this experiment. Leeds provides the radio communication for the detector readout, a huge 3000 km2 local area network, and is involved in the event reconstruction, the data interpretation and the numerical simulation of the experiment.
One of the first array detectors deployed in front of the Andes.