Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8x10^18 eV

SÁNCHEZ, F. (ET. AL, VER PUBLICACION ADJUNTA)

SCIENCE

AMER ASSOC ADVANCEMENT SCIENCE

Año: 2017 vol. 357

0036-8075

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 3x10^4 cosmic rays with energies above 8x10^18 electronvolts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 km2sr 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 anamplitude of 6.5percent toward right ascension a d = 100 degrees and declination24 degrees. That direction indicates an extragalactic origin for these ultrahigh-energy particles.