The Pierre Auger Collaboration, of which the Galician Institute of Hight Energy Physics (IGFAE) is member, is releasing 10% of the data recorded using the world’s largest cosmic ray detector.  These data are being made available publicly with the expectation that they will be used by a wide and diverse community including professional and citizen-scientists and for educational and outreach initiatives. The data can be accessed at

The Pierre Auger Observatory is a collaboration of nearly 400 scientists from more than 90 institutions from 18 countries around the world, including members of the IGFAE, which has participated in the observatory since the 1990s when it was in its design phase. The observatory, which has an area of ​​3,000 km2, operates exclusively with contributions from the participating countries. The contribution of the IGFAE throughout these years was made mostly with the support of the Ministry of Science and Innovation and the Xunta de Galicia.

Results obtained by the observatory has enabled the properties of the highest-energy cosmic rays to be determined with unprecedented precision.  These cosmic rays are predominantly the nuclei of the common elements and reach the Earth from astrophysical sources. The data from the Observatory have been used to show that the highest-energy particles have an extra-galactic origin. The energy spectrum of cosmic rays has been measured beyond 1020 eV, corresponding to a macroscopic value of about 16 joules in a single particle. It has been demonstrated that there is a sharp fall of the flux at high energy, and emerging evidence of emission from particular near-by sources has been uncovered. Analyses of the data have allowed characterisation of the type of particles that carry these remarkable energies, which include elements ranging from hydrogen to silicon. They can be used to test particle physics at energies beyond the reach of the Large Hadron Colllider (LHC) at CERN (Geneve), the largest particle accelerator in the world.

At the Pierre Auger Observatory, located in Argentina, cosmic rays are observed indirectly, through extensive air-showers of secondary particles produced by the interaction of the incoming cosmic ray with the atmosphere. The Surface Detector of the Observatory covers 3000 km² and comprises an array of particle detectors separated by 1500 m. The area is overlooked by a set of telescopes that compose the Fluorescence Detector which is sensitive to the auroral-like light emitted as the air-shower develops, while the Surface Detector is sensitive to muons, electrons and photons that reach the ground. The data from the Observatory comprises the raw ones, obtained directly from these and other instruments, through reconstructed data sets generated by detailed analysis, up to those presented in scientific publications. Some of the data are routinely shared with other observatories to allow analyses with full-sky coverage and to facilitate multi-messenger studies, whose signal can be composed of electromagnetic radiation, gravitational waves or subatomic particles.

As pointed out by the spokesperson, Ralph Engel, “the data from the Pierre Auger Observatory, which was founded more than 20 years ago, are the result of a vast and long-term scientific, human, and financial investment by a large international collaboration. They are of outstanding value to the worldwide scientific community.” By releasing data and analysis programs to the public, the Auger Collaboration upholds the principle that open access to the data will, in the long term, allow the maximum realization of their scientific potential.

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Image: night sky over the Pierre Auger Observatory. Credit: Steven Saffi.