To estimate the energy of any cosmic ray event detected by the Pierre Auger Observatory, the detectors have to be calibrated.
On August 17, 2017 the LIGO and Virgo collaboration measured a gravitational wave originating from a binary neutron star merger.
Ever since the existence of cosmic rays with individual energies of several Joules was established in the 1960s, speculation has raged as to whether cosmic particles of mean energy of 2 Joules are created in our Milky Way or in distant extragalactic objects.
Cosmic rays are mostly charged particles that reach Earth from outer space.
The Pierre Auger Collaboration has investigated the constraining power of the cosmic ray spectrum and composition measurements with respect to the properties of the possible sources.
The Pierre Auger Collaboration has searched for the possible presence of photons with energies exceeding 1018 eV in the flux of cosmic rays arriving at Earth.