Large-scale Anisotropy in the Arrival Directions of Ultra-High Energy Cosmic Rays with the Pierre Auger Observatory
The Pierre Auger Observatory in Argentina is the world's largest observatory for measuring ultra-high energy cosmic rays with an observation area of 3000 km2. The atomic nuclei arriving from outer space reach the highest energies observed in nature. Clues to their origin come from studying the distribution of their arrival directions. We discuss an anisotropy observed at more than the 5 sigma level of significance, which can be described by a dipole signature (Science, Sep 2017, Vol. 357 Iss. 6357, p 1266). We put this observation into the context of searches for cosmic ray origins.