Laboratory Simulation of Blazar Fireballs at CERN Supports Existence of Primordial Cosmic Magnetic Fields

An international collaboration of scientists, spearheaded by experts from Oxford University, has reported a monumental success in laboratory astrophysics. For the first time, researchers managed to replicate the extreme conditions of plasma "fireballs" under precise, controlled laboratory settings. This groundbreaking experiment, conducted at the Super Proton Synchrotron facility at CERN, sought to analyze the stability of high-energy particle jets emitted by blazars. Crucially, the work aimed to shed light on two cosmic puzzles: the puzzling scarcity of gamma-rays and the potential presence of unseen magnetic fields permeating space. The findings were officially documented and published in the journal PNAS on November 3, 2025.

The innovative methodology centered on creating an empirical testbed for hypotheses concerning intergalactic fields by simulating the pair cascades originating from blazars. The research team, featuring Professor Gianluca Gregori, Professor Bob Bingham of the STFC Central Laser Facility, and Professor Subir Sarkar, utilized the specialized HiRadMat apparatus. This setup was employed to generate electron-positron pairs. These pairs were subsequently channeled across a meter-long volume containing ambient plasma, effectively mirroring how blazar emissions propagate through the vast expanse of the intergalactic medium.

The central enigma addressed by the experiment revolved around the inexplicable deficit of gamma-rays measured in the gigaelectronvolt (GeV) energy range. Standard astrophysical calculations predict that these lower-energy GeV rays should be abundantly produced as secondary products resulting from cascades initiated by much higher-energy teraelectronvolt (TeV) rays emitted by blazars. Prior to this study, two primary explanations dominated the discussion. The first posited that weak intergalactic magnetic fields were responsible for deflecting the particle beams. The second suggested that the particle beams themselves suffered from spontaneous instabilities, which would then generate localized magnetic fields capable of scattering the radiation.

Upon analyzing the magnetic signatures and the overall profile of the particle beam, the researchers observed a striking outcome: the electron-positron beam maintained a surprisingly narrow and almost parallel trajectory. This crucial observation indicated a minimal degree of self-interaction and negligible generation of intrinsic magnetic fields by the beam itself. When scaled up to the immense distances of cosmic space, this finding provides compelling evidence that beam-plasma instabilities are simply too minor a factor to account for the observed scarcity of GeV gamma-rays.

Consequently, the stability demonstrated in the laboratory setting significantly bolsters the alternative hypothesis: that intergalactic space is already permeated by a pervasive magnetic field. This field is theorized to be a relic, a remnant inherited directly from the Universe’s infancy. This successful methodology, which translates extreme astrophysical conditions into a terrestrial laboratory environment, represents a major triumph, allowing speculative cosmic models to be tested empirically. Nevertheless, while the experiment successfully ruled out one major theory, it simultaneously deepens the profound mystery surrounding the origin of this primordial magnetic field. Researchers suggest that understanding how this field was initially "seeded" in the early Universe might necessitate a fundamental revision of physics extending beyond the established Standard Model.