The most powerful particle accelerator known to science is not a ring of superconducting magnets on Earth but a pair of stars in the constellation Cygnus. China’s LHAASO observatory has confirmed that the binary system Cygnus X-3 accelerates particles past the 30 PeV threshold, thousands of times beyond the energies the Large Hadron Collider can produce. It is the source of the highest-energy photons ever observed.
Cygnus X-3 is a high-mass X-ray binary: a compact object, most likely a black hole, pulling in a stream of gas from a Wolf-Rayet star companion. It is one of only two known binaries of this type, and it is invisible to the naked eye, shining instead across radio, infrared, X-ray, and gamma-ray wavelengths. Astronomers have long classified it as a microquasar, a small-scale version of the jets seen around supermassive black holes.
In a paper published in the National Science Review, a collaboration led by the Institute of High Energy Physics of the Chinese Academy of Sciences, together with the Tsung-Dao Lee Institute in Shanghai and the Shanghai Astronomical Observatory, reports LHAASO observations of intense flaring in ultra-high-energy gamma emission from the system. The flares correlated in time with GeV-band emission a million times lower in energy: during the active periods, both the Fermi satellite and LHAASO detected highly significant signals, while LHAASO saw nothing during quiet stretches.
The timing of the signal carried the key clue. The emission pulsed with a period of 4.8 hours, matching the orbital period of the binary, which allowed the team to place the accelerator within a region about three times as wide as the Sun. That is the most precise localization of an ultra-high-energy accelerator ever obtained, and it makes Cygnus X-3 the first confirmed case of an ultra-high-energy gamma-ray emitter that varies over time.
The discovery opens a new line of astronomy: ultra-high-energy time-domain science, in which cosmic accelerators are studied as they switch on and off rather than as static sources. It also offers a fresh window into the physics near black holes, where particles are boosted to energies far beyond any theoretical expectation for such systems. The results carry implications for multi-messenger astronomy, since cosmic rays produced in extreme environments like this one may eventually be traced back to their sources; the author list includes Felix Aharonian, a leading figure in high-energy astrophysics.
The detection showcases LHAASO itself. The observatory, located at 4,410 meters above sea level in Daocheng, Sichuan, has been catching air showers produced by cosmic gamma rays and particles since April 2019. Confirming a variable source at petaelectronvolt energies, well above what theory predicted for this class of object, demonstrates the niche such wide-field detectors fill: catching the most extreme accelerators in the universe as they flare.
Sources: Variable super-PeVatron located in Cygnus X-3, opening a new window for ultra-high-energy time-domain astronomy (EurekAlert/Science China Press, Jul 26, 2026); Cygnus X-3 confirmed as universe’s most powerful particle accelerator at 30 PeV: LHAASO (Interesting Engineering, Aug 3, 2026); Cygnus X-3 confirmed as universe’s most powerful particle accelerator at 30 PeV – LHAASO (MSN, Aug 2026); China discovers universe’s most powerful particle accelerator (Qazinform/Xinhua, 2026)