China’s underground neutrino lab JUNO begins hunt for ghost particles

China’s Jiangmen Underground Neutrino Observatory (JUNO) officially began data collection on August 26, 2025, after more than a decade of development. Located 700 meters underground to shield it from cosmic rays, JUNO features a massive 35.4-meter diameter acrylic sphere filled with 20,000 tons of liquid scintillator. This detector is designed to capture faint flashes of light produced when antineutrinos interact with the liquid, with tens of thousands of photomultiplier tubes converting these signals into data for analysis. JUNO’s primary scientific goal is to resolve the long-standing mystery of neutrino mass ordering—determining which of the three neutrino types is heaviest or lightest—by precisely measuring the energy spectrum of antineutrinos. Beyond neutrino mass ordering, JUNO aims to deliver highly precise measurements of neutrino properties and explore a range of phenomena, including neutrinos from the Sun and supernovae, potential new neutrino types, and