High-energy cosmic neutrino detected under Mediterranean Sea

Scientists detect record-breaking energy neutrino from beyond Milky Way, offering insight into universe's cataclysmic events.

Using an observatory under construction deep beneath the Mediterranean Sea near Sicily, scientists have detected a ghostly subatomic particle called a neutrino boasting record-breaking energy in another 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 actively guzzling surrounding matter at the center of distant galaxies as possible origination points, though the neutrino may have arisen from some other source.

KM3NeT comprises two large neutrino detectors at the bottom of the Mediterranean. One called ARCA - 3.4 km deep near Sicily - is designed to find high-energy neutrinos. One called ORCA - 2.4 km deep near Provence, France - is designed to detect low-energy neutrinos.

The newly described "ultra-high energy" neutrino, detected by ARCA in February 2023, was measured at about 120 quadrillion electronvolts, a unit of energy.

It was 30 times more energetic than any other neutrino detected to date, a quadrillion times more energetic than particles of light called photons and 10,000 times more energetic than particles made by the world's largest and most powerful particle accelerator, the Large Hadron Collider near Geneva.

"It's in a completely unexplored region of energy," said physicist Paschal Coyle of the Marseille Particle Physics Centre (CPPM) in France, one of the leaders of the research published on Wednesday in the journal Nature.

"The energy of this neutrino is exceptional," added physicist Aart Heijboer of the Nikhef National Institute for Subatomic Physics in the Netherlands, another of the researchers.