Although construction of the Pierre Auger Observatory will not be completed until March 2008, the modular nature of the instrument has made it already possible to acquire significant astrophysical information. References to published work are listed under References.

Two very important results have been reported recently:
(i) the observation that the highest energy particles are of extragalactic origin (and may originate in Active Galactic Nuclei) [3],
 and
(ii) the finding that the energy spectrum of cosmic rays steepens above an energy of 4 x 10¹⁹ eV [4].
 
These two results, taken together, suggest that the Greisen-Zatsepin-Kuz’min effect, predicted in 1996, has finally been observed.  Thus we can conclude that the bulk of the highest energy cosmic rays come from within about 300 million light years from earth, very close by on the cosmological distance scale. (Exotic Physics and Astrophysics).

Two other important results have been published relating to the search for signals from the centre of our Galaxy and to the search for photons above 10¹⁸ eV in the general cosmic ray flux. 
A search for signals from the centre of our Galaxy was made because it has been suggested that the black hole there could accelerate high energy cosmic rays and, through interactions with gas and photons close to the black hole, neutrons might be created.   At rest, the neutron has a mean lifetime of about 15 minutes but because of time dilation a neutron of 10¹⁸ eV can travel, on average, ~ 1 kpc or 3 light years before decay.  Previous studies have suggested that emission of cosmic rays was detectable from the Galactic Centre.  No confirmation of the earlier results has been possible and we are only able to put limits of ~ 0.05 km^-2 yr^-1 on the flux of particles from the Galactic Centre, much lower than claimed before [2]. 

The search for high energy photons was motivated as a consequence of discussions of exotic explanations for the origin of the highest energy cosmic rays.  One such explanation supposes the existence of very massive particles created in the early Universe when it was very hot.  These particles are predicted to decay to give cosmic rays.  However such an explanation predicts large numbers of photons at the highest energies but this is not found from the studies made at the Pierre Auger Observatory.  High energy neutrinos are also expected from such processes: the results of our search for neutrinos will be reported in 2008 [1].