Scientists Identify Blazars as Source of Universe's Most Powerful Neutrino Ever Detected
Researchers believe the record-breaking 220 PeV particle detected in the Mediterranean Sea originated from supermassive black holes shooting jets directly toward Earth.
Scientists may have solved one of the most intriguing cosmic mysteries in recent years by identifying the likely source of the most energetic neutrino ever detected. The extraordinary particle, which slammed through the Mediterranean Sea three years ago with an energy of around 220 PeV—more than ten times greater than previously detected high-energy neutrinos—appears to have originated from blazars, some of the universe's most extreme objects.
The groundbreaking neutrino was detected on February 13, 2023, by the KM3NeT/ARCA observatory located deep off the coast of Sicily. Remarkably, the detector captured this record-breaking signal while still under construction, operating with only 21 detection lines representing about 10 percent of the observatory's planned final configuration. The detection immediately sparked an intensive investigation to determine the particle's cosmic origin.
Blazars are active galactic nuclei powered by supermassive black holes that shoot enormous jets of plasma directly toward Earth. These cosmic powerhouses are capable of accelerating particles to extreme energies, making them prime candidates for producing the universe's most energetic neutrinos. The new research, published in the Journal of Cosmology and Astroparticle Physics, suggests the particle came from a population of these extreme accelerators rather than a single dramatic cosmic event.
"There are several possible explanations for the origin of this particle," explains Meriem Bendahman, a researcher at INFN Naples and member of the KM3NeT collaboration. "For example, it has been proposed that such neutrinos are generated when ultra-high-energy cosmic rays interact with the cosmic microwave background radiation. But there is also the possibility that the neutrino originates from a diffuse flux produced by a population of extreme accelerators, such as blazars."
The investigation resembled forensic detective work, with scientists creating detailed simulations and comparing results with actual observations. Unlike many cosmic events where astronomers can identify electromagnetic counterparts such as radio waves or gamma rays, this neutrino detection showed no matching signal from the same region of space. This absence of a corresponding electromagnetic signature led researchers to consider that the particle emerged from a diffuse background of many sources rather than a single point-like event, strengthening the case for blazar populations as the culprits behind this cosmic record-breaker.
