The Jiangmen Underground Neutrino Observatory (JUNO) officially commenced operations in August 2025, marking a significant advancement in the study of neutrinos. Situated 700 meters underground in China's Guangdong Province, this state-of-the-art facility is dedicated to the intricate study of neutrinos, elusive subatomic particles that interact minimally with matter. JUNO's primary mission is to precisely determine the neutrino mass hierarchy and measure oscillation parameters, which are crucial for understanding the fundamental building blocks of the universe.
The observatory features a colossal liquid scintillator detector, weighing 20,000 tons, housed within a 35.4-meter-diameter acrylic sphere. This entire setup is submerged in a vast, 12-story-tall tank of water, creating an exceptionally low-interference environment optimized for capturing neutrinos. The detector is equipped with approximately 45,000 photomultiplier tubes, acting as highly sensitive detectors for the faint light signals produced when neutrinos interact with the scintillator material. The development of critical components, such as the metal film for the photomultiplier tubes, represents a significant independent technological achievement by Chinese scientists, drastically reducing costs.
The realization of the JUNO observatory is the culmination of over a decade of work, with an investment exceeding $300 million. This ambitious project has fostered a substantial international collaboration, uniting approximately 700 scientists from 74 research institutions across 17 countries and regions. The observatory is projected to operate for a minimum of 30 years. Construction of the facility began in January 2015. JUNO's unique location, 53 kilometers from both the Yangjiang and Taishan nuclear power plants, provides an ideal baseline for its primary scientific objectives.
The commencement of operations in August 2025 marks the world's first ultra-large-scale, ultra-high-precision neutrino-dedicated scientific facility to go live, setting a new benchmark in experimental physics. JUNO's findings are anticipated to have a transformative impact on the field, potentially paving the way for discoveries that could redefine our understanding of the universe.