Ultra-high energy cosmic rays are the most energetic particles known in Nature, and we are part of a large international collaboration formed to determine the origin of these particles. The cosmic rays of interest are incredibly energetic (in excess of 10^19 electron-volts) but they are also incredibly rare (less than 1 particle per square kilometre per year), so detectors must be large.
The Pierre Auger Observatory, situated in western Argentina, monitors an area of 3,000 square kilometres 24 hours per day looking for interactions of the highest energy cosmic rays. We are building up a large data set that will allow us to identify likely astrophysical sources of these particles, and to understand the extreme processes which accelerate the particles to enormous energies.
Our specific contributions to the Pierre Auger Observatory include leadership in the analysis of data from the air fluorescence detectors of Auger, monitoring the 3,000 square kilometres of area for night-time cloud, and in the astrophysical interpretation of the data through arrival direction and mass composition studies. Further details can be found at the Adelaide astrophysics home page at https://physsci.adelaide.edu.au/astrophysics/