The origin of ultra energetic cosmic rays has been a mystery over the past 50 years. On September 2017, the Pierre Auger Observatory reported an anisotropy in the 3 x 10^4 cosmic rays recorded with energies above 8 x 10^8 eV. This anisotropy, detected with a significance above 5.2σ, indicates an extragalactic origin for these particles; that is, they are likely to be produced far away from our galaxy.
Physicists build powerful underground accelerators, such as the Large Hadron Collider (LHC), located in the French-Swiss border, to study particle properties with the aim of understanding the fundamental questions about matter and the Universe. Yet, the most energetic particles we have ever observed come from the sky, from sources we still know very little about.
The Square Kilometre Array (SKA) will be a multi-purpose radio-interferometer with a collecting area of 1 square kilometre, distributed over a distance of at least 3000 km, co-located in Africa and Australia.
