Scientists working with a massive underground detector in China have released the first major findings from a project aimed at unlocking the secrets of neutrinos, elusive particles that have puzzled physicists for decades.
The Jiangmen Underground Neutrino Observatory, known as JUNO, began collecting data in August 2025 after more than a decade of planning and construction. Researchers published the detector’s initial results Wednesday in the journal Nature, drawing on data gathered during its first two months of operation.
The findings include some of the most precise measurements yet of how neutrinos change between three different forms, or flavors, as they travel through space.
Neutrinos, often called “ghost particles,” are believed to have existed since the Big Bang. Trillions pass through the human body every second, yet they rarely interact with matter and possess extremely small masses, making them difficult to study.
“It really makes me look forward to more exciting results in the future,” said physicist Kate Scholberg of Duke University, who was not involved in the research, per The Associated Press.
Located 2,297 feet (700 meters) underground in Guangdong Province, JUNO is the world’s largest transparent spherical detector and the first operational ultra-large facility dedicated to ultra-high-precision neutrino research. At its center is a 20,000-ton liquid scintillator detector designed to capture faint signals produced when antineutrinos interact with particles inside the instrument.
The observatory monitors antineutrinos generated by nuclear reactions at the nearby Taishan and Yangjiang nuclear power plants. When those particles collide with material inside the detector, they produce tiny flashes of light that can be recorded and analyzed.
Researchers hope the facility will help answer one of the most important unresolved questions in particle physics: the ordering of neutrino masses. Scientists believe two neutrino flavors have similar masses while a third differs, but they do not yet know whether the oddball particle is the heaviest or the lightest of the three.
The newly published results do not resolve that question, but researchers say they demonstrate the detector’s precision and ability to probe the subtle differences among neutrino types.
The results show that JUNO “will be able to test the finer ripples” that distinguish neutrino flavors and masses, said study co-author Liangjian Wen, a member of the JUNO collaboration, per AP.
The facility was proposed in 2008 and approved in 2013 before underground construction began in 2015. Detector installation was completed in late 2024, and trial operations showed performance indicators met or exceeded design expectations.
“Completing the filling of the JUNO detector [with ultra-pure water] and starting data taking mark a historic milestone. For the first time, we have put into operation a detector of this scale and precision dedicated to neutrinos. JUNO will allow us to answer fundamental questions about the nature of matter and the universe,” Wang Yifang, spokesperson for JUNO and a researcher at the Chinese Academy of Sciences’ Institute of High Energy Physics, said in 2025.
The international project involves more than 700 researchers from 74 institutions across 17 countries and regions. Scientists say the observatory is expected to operate for up to 30 years and could eventually help answer broader questions about particle physics, astrophysics and cosmology.
“Building JUNO has been a journey of extraordinary challenges. It demanded not only new ideas and technologies, but also years of careful planning, testing, and perseverance,” said Ma Xiaoyan, the project’s chief engineer.
Future results from JUNO are expected to be compared with findings from two other major neutrino experiments now under development: Japan’s Hyper-Kamiokande detector and the U.S.-based Deep Underground Neutrino Experiment, both of which are targeted to begin collecting data within the next decade.
Together, the projects aim to provide a clearer picture of some of the universe’s most mysterious particles and the role they play in the fundamental structure of matter.
