NEW YORK (AP) — A neutrino detector submerged in the Mediterranean Sea has sniffed out the most energetic ghost particle yet, scientists reported Wednesday. The newly detected neutrino is around 30 times more active than the previous recordholder. Scientists think it came from outside the Milky Way galaxy but its exact source remains a mystery.

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 kilometer cubic neutrino telescope (KM3NeT) in the deep sea.

The KM3NeT telescope comprises two detectors, ARCA and ORCA, utilizing seawater to capture Cherenkov light—a bluish glow produced when neutrinos interact with water molecules.