Pierre Auger Observatory

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Observatory

SD Tank of the Pierre Auger Observatory in Malargüe, Mendoza Province near the Andes range

Back view of a tank

Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra high energy cosmic rays -- Ultra-high-energy particles. These are sub-atomic particles (protons or other nuclei) with energies beyond $1020$ electron-volts, the energy of a tennis ball traveling at 50 miles per hour, but packed into a single subatomic particle. These high energy particles have an estimated arrival rate of just 1 per square kilometer per century, therefore, in order to record a large number of these events, the Auger Observatory has created a detection area the size of Rhode Island in western Argentina's Mendoza Province.

The observatory was named after the French physicist Pierre Victor Auger. The observatory project was proposed in 1992 by Jim Cronin and Alan Watson. Today, more than 200 physicists from 55 institutions around the world are collaborating to build the southern site. The 15 participating countries are sharing the $50 million construction budget, each providing a minor part of the total cost.

The observatory will consist of northern and southern sites. The southern site is in the final phase of construction and is currently operating and collecting data. It became the largest ultra-high energy cosmic ray detector in the world in 2003. It is located on the vast plain of Pampa Amarilla, near the town of Malargüe in Mendoza Province, Argentina. The northern site will be located in southeastern Colorado, United States and hosted by Lamar Community College. Each site of the final observatory will consist of 1600 water tanks (Water Cherenkov Detectors) distributed over 3000 km² (similar to the Haverah Park experiment) overseen by four atmospheric fluorescence detectors similar to the High Resolution Fly's Eye.

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 3 large photomultiplier tubes to detect the light 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 dark 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.[Science Magazine; 9 November 2007; The Pierre Auger Collaboration et al., pp. 938 - 943]

[edit] Stamps

Argentina issued 100,000 postage stamps honouring the observatory on 14 July 2007. The stamp shows a surface detector tank in the foreground, a building of fluorescence detectors in the background, and the expression " $1020$ eV" in large lettering. [1] [2]