The energy spectrum of the highest-energy particles in the Universe, ultra-high energy cosmic rays, has been measured with the Pierre Auger Observatory with an unprecedented precision. In addition to the well-known kink in the energy spectrum, typically referred to as the ankle, a new spectral break is found at somewhat higher energy. This new break in the energy spectrum can be explained by an energy-dependent mass composition of cosmic rays. The results are published in two related papers (Phys. Rev. Lett. 125, 121106 (2020) and Phys. Rev. D 102, 062005 (2020)).
On 19 December 2018, the Cherenkov Telescope Array Observatory (CTAO) and the European Southern Observatory (ESO) signed the final agreements needed for CTA’s southern hemisphere array to be hosted near ESO’s Paranal Observatory in Chile. With these agreements in place, the CTAO will be able to begin construction on the southern site. The hosting agreement with the Instituto de Astrofísica de Canarias (IAC) is already in place to host CTA’s northern hemisphere array at the Observatorio del Roque de los Muchachos in La Palma, Spain.
