On February 13, 2023, the ARCA (Astroparticle Research with Cosmics in the Abyss) component of the kilometre cubic neutrino telescope (KM3NeT) made an extraordinary observation, detecting a neutrino with an estimated energy of approximately 220 PeV. This remarkable event, designated KM3-230213A, is recorded as the highest-energy neutrino ever documented. Neutrinos are incredibly plentiful throughout the cosmos, yet they interact with matter on such a minimal level that capturing their interactions demands immense detector systems. The findings related to this event were published in the esteemed journal Nature.

Similar to conventional telescopes, KM3NeT leverages neutrino detection to gather insights about distant cosmic entities and phenomena, including our own Sun, various solar systems, and far-off galaxies. Due to the subdued interaction properties of neutrinos, they cannot be observed directly like light, but are instead detected indirectly through devices such as photomultipliers. These devices capture the faint bluish light produced by Cherenkov radiation when a neutrino interacts with a dense medium, such as the deep sea water surrounding the ARCA facility. This advanced detector is positioned 3,450 meters below the surface, off the coast of Sicily, featuring detection units (DUs) that soar to 700 meters tall and are spaced 100 meters apart, comprising numerous spheres filled with sophisticated sensors and operational equipment.

While identifying the precise source or location of this high-energy neutrino remains challenging from a single observation, each subsequent detection will enhance our understanding of its origins. Additionally, this significant discovery marks a promising milestone for the relatively new neutrino telescope initiative, which is still in development. More detection units are being systematically installed near the shores of France and Greece, expanding the telescope’s capability to capture more neutrino events.