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From galaxies far far away!


In a paper to be published in Science on 22 September, the Pierre Auger Collaboration reports observational evidence demonstrating that cosmic rays with energies a million times greater than that of the protons accelerated in the Large Hadron Collider come from much further away than from our own Galaxy. Ever since the existence of cosmic rays with individual energies of several Joules was established in the 1960s, speculation has raged as to whether such particles are created there or in distant extragalactic objects. The 50 year-old mystery has been solved using cosmic particles of mean energy of 2 Joules recorded with the largest cosmic-ray observatory ever built, the Pierre Auger Observatory in Argentina. It is found that at these energies the rate of arrival of cosmic rays is 6% greater from one half of the sky than from the opposite one, with the excess lying 120˚ away from the Galactic centre.

It should be noted that this remarkable paper owes a lot to three researchers from out laboratory, corresponding authors : Olivier Deligny, working for many years in the search of anisotropies on arrival directions of cosmic rays, work that led to that discovery ; Piera Luisa Ghia and Jonathan Biteau, member of the editorial board for this paper.


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au CNRS-IN2P3 : Institut de physique nucléaire d’Orsay (CNRS/Université Paris-Sud), Laboratoire de physique nucléaire et des hautes énergies (CNRS/UPMC/ Université Paris Diderot), Laboratoire de physique subatomique et de cosmologie (CNRS/Université Grenoble Alpes/Grenoble INP)


 

IPN

Institut de Physique Nucléaire Orsay - 15 rue Georges CLEMENCEAU - 91406 ORSAY (FRANCE)
UMR 8608 - CNRS/IN2P3

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