Pierre Auger Observatory - Overview

Overview

The observatory has been taking production-grade data since 2005 and was officially completed in 2008. In 2003, it became the largest ultra-high energy cosmic ray detector in the world. It is located on the vast plain of Pampa Amarilla, near the town of Malargüe in Mendoza Province, Argentina. The basic set-up consists of 1600 stations (water Cherenkov Detectors, similar to the Haverah Park experiment) distributed over 3,000 square kilometres (1,200 sq mi), along with four atmospheric fluorescence detectors (similar to the High Resolution Fly's Eye) overseeing the surface array. Work is ongoing on upgrades to the observatory, including:

• three additional fluorescence telescopes, capable of covering higher altitudes (HEAT — High Elevation Auger Telescopes)
• two higher-density nested arrays of surface detectors combined with underground muon counters (AMIGA — Auger Muons and Infill for the Ground Array)
• a prototype radiotelescope array (AERA — Auger Engineering Radio Array) for detecting radioemission from the shower cascade, in the frequency range 30-80 MHz
• R&D on detecting microwave emission from shower electrons (frequencies around 4 GHz)

The Pierre Auger Observatory is unique in that it is the first experiment that combines both ground and fluorescence detectors at the same site thus allowing cross-calibration and reduction of systematic effects that may be peculiar to each technique. The Cherenkov detectors use three large photomultiplier tubes to detect the Cherenkov radiation produced by high-energy particles passing through water in the tank. The time of arrival of high-energy particles from the same shower at several tanks is used to calculate the direction of travel of the original particle. The fluorescence detectors are used to track the particle shower's glow on cloudless moonless nights, as it descends through the atmosphere.

The Pierre Auger Collaboration has made available (for outreach purposes) 1% of the full ground array data set. This data can be explored at the Public Event Display web site.

In November 2007, it was announced that the observatory had found a correlation between the 27 highest energy events and nearby active galactic nuclei (AGN). This would suggest that these events are triggered by protons that were emitted by objects correlated with the AGN distribution of matter. Acceleration by the large magnetic fields associated with the massive central black holes that form the AGNs is one possibility.