Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 × 1018 eV

THE PIERRE AUGER COLLABORATION; MOLLERACH, SILVIA

Science

American Association for the Advancement of Science

Año: 2017 vol. 357 p. 1266 - 1270

Cosmic rays are atomic nuclei arriving from outer space that reach the highest energiesobserved in nature. Clues to their origin come from studying the distribution of theirarrival directions. Using 3 × 10 4 cosmic rays with energies above 8 × 10 18 electronvolts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 km 2sr year, we determined the existence of anisotropy in arrival directions. The anisotropy,detected at more than a 5.2s level of significance, can be described by a dipole with anþ1:3amplitude of 6:5 0:9percent toward right ascension a d = 100 ± 10 degrees and declinationþ12d d = 24 13 degrees. That direction indicates an extragalactic origin for these ultrahigh-energy particles.