Using an observatory under construction deep beneath the Mediterranean Sea near Sicily, scientists have detected a ghostly subatomic particle called a neutrino with record-breaking energy. This discovery marks an important step toward understanding some of the universe's most cataclysmic events.The researchers, part of the KM3NeT (Cubic Kilometre Neutrino Telescope) Collaboration, believe the neutrino came from beyond the Milky Way galaxy. They identified 12 supermassive black holes at the centers of distant galaxies as possible sources, though other origins remain possible.KM3NeT comprises two large neutrino detectors at the bottom of the Mediterranean. One called ARCA, 3,450 meters deep near Sicily, is designed to find high-energy neutrinos. Another, called ORCA, 2,450 meters deep near Provence, France, detects low-energy neutrinos.The "ultra-high energy" neutrino detected by ARCA in February 2023 was measured at about 120 quadrillion electronvolts, making it 30 times more energetic than any previously detected neutrino. It was also a quadrillion times more energetic than photons and 10,000 times more energetic than particles produced at the Large Hadron Collider near Geneva.Physicist Paschal Coyle of the Marseille Particle Physics Centre described this energy level as "completely unexplored." Aart Heijboer of the Nikhef National Institute for Subatomic Physics called it "exceptional."Neutrinos are unique cosmic messengers, as they travel unimpeded through matter and can be traced back to their source, helping scientists study the most energetic processes in the cosmos. Unlike cosmic rays, whose paths are bent by magnetic fields, neutrinos travel straight, making them more reliable for studying deep-space phenomena.Detecting neutrinos is challenging and requires large underwater or ice-based observatories. These environments allow scientists to detect flashes of Cherenkov radiation produced when a neutrino interacts with a particle.The researchers concluded that the neutrino detected at ARCA—a muon neutrino—was of cosmic origin due to its horizontal trajectory and the fact that it had traveled through 140 km of rock and seawater before reaching the detector.
