Mediterranean Sea Reveals Most Energetic Neutrino Ever Detected

In early 2023, the Cubic Kilometre Neutrino Telescope (KM3NeT), located off the coast of Toulon, France, detected a neutrino with unprecedented energy. Dubbed KM3-230213A, this "ghost particle" released at least 20 times more energy than any other neutrino previously observed, reaching approximately 220 petaelectronvolts (PeV). The findings were published in *Nature*. Neutrinos, the smallest and lightest particles known, possess no electric charge and can traverse planets unimpeded. KM3NeT, a telescope submerged thousands of meters underwater, captured the neutrino's signature as flashes of light. The detected neutrino had an energy equivalent to more than 15 times the maximum energy achieved in the Large Hadron Collider (LHC) at CERN. Scientists are currently investigating the origin of KM3-230213A, considering possibilities such as a violent supermassive black hole (blazar) or a cosmogenic neutrino formed from high-energy cosmic rays interacting with low-energy photons. If confirmed as a cosmogenic neutrino, it would mark the first discovery of its kind. The KM3NeT collaboration, involving over 360 scientists from 68 institutions across 21 countries, continues to expand the detector to enhance sensitivity and gather more data. This discovery opens a new window into the universe's most energetic phenomena, potentially revealing insights into supermassive black holes, supernovas, and gamma-ray bursts. The detection of such high-energy neutrinos could also provide unique information about the mechanisms involved in the most energetic phenomena of the cosmos.