KM3NeT DETECTS THE HIGHEST ENERGY NEUTRINO EVER OBSERVED
The KM3NeT Collaboration announces the detection from the abyss of the Mediterranean Sea of a cosmic neutrino with a record-breaking energy of about 220 PeV
An extraordinary event consistent with a neutrino with an estimated energy of about 220 PeV (220 x 1015 electron volts or 220 million billion electron volts), was detected on February 13, 2023, by the ARCA detector of the kilometre cubic neutrino telescope (KM3NeT) in the deep sea. This event, named KM3-230213A, is the most energetic neutrino ever observed and provides the first evidence that neutrinos of such high energies are produced in the Universe. After long and meticulous work to analyse and interpret the experimental data, today, February 12, 2025, the international scientific collaboration of KM3NeT reports the details of this amazing discovery in an article published in Nature.
The detected event was identified as a single muon which crossed the entire detector, inducing signals in more than one third of the active sensors. The inclination of its trajectory combined with its enormous energy provides compelling evidence that the muon originated from a cosmic neutrino interacting in the vicinity of the detector.
“KM3NeT has begun to probe a range of energy and sensitivity where detected neutrinos may originate from extreme astrophysical phenomena. This first ever detection of a neutrino of hundreds of PeV opens a new chapter in neutrino astronomy and a new observational window on the Universe”, comments Paschal Coyle, KM3NeT Spokesperson at the time of the detection.
What makes this event special?
The detection of KM3-230213A is ground-breaking for several reasons:
- Unprecedented Energy: Such high-energy neutrinos are extremely rare, making this a monumental discovery.
- Precision Detection: The advanced design of the ARCA detector, featuring multi-photomultiplier optical modules with nanosecond timing precision, enabled precise reconstruction of the neutrino’s trajectory and energy. Its near-horizontal path through the detector indicates a cosmic origin, as atmospheric muons cannot travel such long distances through the seawater without being absorbed.
- Cosmic Origins: This neutrino might originate from a powerful cosmic accelerator, such as an active galactic nucleus or a gamma-ray burst. Alternatively, it could be a cosmogenic neutrino, produced in the interaction between an ultra-high-energy cosmic ray with the background radiation in the universe.
Searching for the source
After detecting KM3-230213A, the KM3NeT scientists analysed its direction and energy to identify its possible astrophysical origin. Researchers cross-referenced data from gamma-ray, X-ray, and radio telescopes to look for potential counterparts, such as blazars or transient events. While its arrival direction aligns with regions containing active cosmic phenomena, no definitive source could be significantly identified.
Even though an extragalactic origin is most likely, the event’s position near the Galactic plane does not exclude the possibility it originated in our Milky Way.
This highlights the challenge of linking single neutrino detections to specific astrophysical sources.
Its importance for neutrino astronomy
This discovery marks a milestone in neutrino astronomy, a field still in its infancy compared to traditional optical or radio astronomy. High-energy neutrino observations like KM3-230213A offer unique insights into the most extreme environments in the universe. They may help answer long-standing questions about the origins of cosmic rays and how they can be accelerated to such enormous energies.
Furthermore, KM3-230213A provides valuable data to refine models of cosmic neutrino production and propagation. It also demonstrates the capabilities of next-generation observatories like KM3NeT, which continue to push the boundaries of our understanding.
The road ahead
While KM3-230213A raises many questions, it also opens new doors. Future observations will focus on detecting more such events to build a clearer picture of their origins. The ongoing expansion of KM3NeT with additional detection lines and increasing data taking time will improve its sensitivity and enhance its ability to pinpoint neutrino sources.
The evidence of this ultra-high-energy cosmic neutrino is a testament to human ingenuity and the enduring quest to understand the universe. Each neutrino captured is like a piece of a jigsaw puzzle, revealing a bit more about the cosmos. As technology advances, we are poised to discover even more extraordinary phenomena in the vast expanse of space.