Timeline of the Pierre Auger Observatory



The Pierre Auger Observatory was conceived by Jim Cronin and Alan Watson at the 1991 International Cosmic Ray Conference in Dublin to address the mysteries of the origin and nature of the highest-energy cosmic rays.  It was clear to them that only a very large detector would have the exposure to collect enough events to answer to the questions raised by a century of earlier experiments. The Observatory design evolved into a “hybrid” detector system consisting of a 3000 km2 array of 1660 particle detectors overlooked by 27 optical telescopes. These complementary detector techniques would record both the particles and the faint fluorescence light resulting from the particle cascade initiated in the atmosphere by these mysterious cosmic rays.


Jim W. Cronin and Alan A. Watson suggest building a giant air shower array with much greater collecting power than had ever been considered previously.


January 30 – July 31: Production of a design report – reference design and cost estimate – by the Design Group for the Auger Project hosted by Fermilab, Illinois, USA. This becomes the basis for funding proposals in 17 participating countries.


November: A meeting is held in Paris to form the collaboration. It chooses the site of Mendoza, Argentina in the Southern Hemisphere. The Observatory is named after the French physicist Pierre Victor Auger.


March: Signature of the International Agreement in Mendoza.


Beginning of the construction of the observatory.


The Engineering Array – a full-scale prototype of the first 32 SD stations and a single fluorescence telescope – is operated for 6 months. It is later integrated into the main setup and used for more detailed design choices and calibration.


The Observatory becomes the largest detector in the world for the detection of ultra-high energy cosmic rays.


First physics results are reported from more than 100 surface detector stations.


May: Release of 1% of the data to the public for outreach purposes. The data can be explored at the website of the Public Event Explorer.


November: Preliminary results indicate that the directions of origin of the 27 highest-energy events are correlated with the locations of active galactic nuclei (AGNs).


Observation of the energy spectrum of cosmic rays confirmes that the flux is strongly suppressed above 4.1019 eV as predicted by the GZK theory.

November: Inauguration in Malargüe


Best present limits are set on the detection of photons with an energy of 1018 eV.


Observations of the depth of the maximum of air-shower profiles above 1018 eV give first hints on the composition of cosmic rays at ultra-high energy.


Solar physics with the Auger Observatory.


Measurement of the proton-proton cross section at a centre-of-mass energy of 57 TeV, complementing results from the LHC – always below 14 TeV.


Best present limits on the detection of neutrinos with an energy of 1018 eV.


Observation of large-scale anisotropies: Arrival directions of cosmic rays are not evenly distributed, giving hints on the origin – whether galactic or extragalactic – of cosmic rays at ultra-high energy.


Observations of a deficit in the number of muons in air showers challenge predictions from hadronic interaction models.


November: AugerPrime – Celebrate 15 years of achievements and signature ceremony of a new International Agreement for the next ten years.

Observatorio Pierre Auger
Av. San Martín Norte 304
Malargüe, Mendoza, Argentina

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