This discovery reveals that the peculiar binary system Cygnus X-3 in the constellation Cygnus is the most powerful particle accelerator known to date, capable of producing the highest-energy photons ever observed. The precise temporal variability, ultra-high gamma-ray energies, and spectral characteristics measured by LHAASO collectively confirm this object as the source of cosmic rays, with particle energies reaching at least 30 PeV —far exceeding current theoretical expectations. The study was completed through collaboration among scientists from the Institute of High Energy Physics (Chinese Academy of Sciences), the Tsung-Dao Lee Institute at Shanghai Jiao Tong University, the Shanghai Astronomical Observatory (Chinese Academy of Sciences), and other research institutions. The results were published in 2026 in the National Science Review under the title "Cygnus X-3: A variable petaelectronvolt γ-ray source," with corresponding authors including Professor Zhen Cao, Associate Researcher Cong Li, Associate Professor Jieshuang Wang, Associate Researcher Jianeng Zhou, and Professor Felix Aharonian.
LHAASO detected pronounced flaring activity in ultra-high-energy gamma rays, which showed a clear temporal correlation with observations at the GeV band—one million times lower in energy. During the flaring periods, both the Fermi satellite detector (USA) and LHAASO simultaneously detected highly significant signals, while no signals were observed during quiescent periods for LHAASO. Furthermore, the signal exhibited a 4.8-hour periodicity, also simultaneously detected, clearly reflecting the orbital modulation of the binary system. This allowed the accelerator to be localized within a region roughly three times the size of the Sun—the highest-precision localization ever achieved for an ultra-high-energy particle accelerator in the cosmos.
By confirming Cygnus X-3 as the first ultra-high-energy gamma-ray source with temporal variability, this work opens a new frontier in ultra-high-energy time-domain astronomy and provides a novel avenue for studying the physical processes near compact objects such as black holes. As an extreme cosmic ray accelerator, Cygnus X-3 also has important implication for future multi-messenger astronomy research.
The results have already attracted significant attention in the astrophysics community and have become one of the most hotly discussed topics at international conferences. Within just six months of being posted on the preprint server, the paper has already received nearly 20 citations.
National Science Review