The highest-energy particle ever

On 12 February 2025, the KM3NeT neutrino experiment announced the discovery of the highest-energy particle ever observed by physicists. The particle’s impact induced signals in more than a third of the active sensors in the enormous undersea detector on the seabed of the Mediterranean Sea. The observation of a cosmic neutrino with an estimated energy of 220 million billion electron volts made the front cover of Nature magazine and was reported in countless media outlets. The energy measured is more than ten thousand times greater than that achieved by the largest accelerators on Earth; the cosmic origin of the neutrino has not been traced. 

Dutch scientists and engineers were closely involved in the discovery using the KM3NeT neutrino telescope, currently under construction, a system comprising hundreds of light sensors located kilometres underground. 

From the Netherlands, the NWO institute Nikhef, the University of Amsterdam, Leiden University and NIOZ are members of the KM3NeT collaboration.