Scientists Uncover the Mystery of Space's Hidden Magnets: A Revolutionary Discovery
In a groundbreaking experiment, scientists have crafted the world's first plasma fireballs in a lab setting using the Super Proton Synchrotron accelerator at CERN, Geneva. This achievement marks a significant milestone in unraveling the enigma of the universe's hidden magnetic fields and missing gamma rays.
Led by Professor Gianluca Gregori from the University of Oxford, an international team of researchers embarked on this mission to solve a long-standing puzzle. The focus was on blazars, active galaxies with supermassive black holes that launch powerful particle jets.
These jets emit extremely high-energy gamma rays (TeV), which, as they traverse space, create a cascade of electron-positron pairs. These pairs are expected to scatter off the cosmic microwave background and produce lower-energy gamma rays in the GeV range. However, telescopes like Fermi consistently fail to detect these GeV rays, sparking two main hypotheses.
The first hypothesis suggests that weak intergalactic magnetic fields deflect the pairs, steering the GeV rays away from Earth. The second hypothesis posits that the electron-positron pair beams become unstable as they travel, generating internal magnetic fields that dissipate the beam's energy before GeV rays can be produced.
To test these theories, the researchers utilized CERN's HiRadMat facility and the Super Proton Synchrotron to generate and accelerate electron-positron pairs through a meter of plasma. The experiment successfully replicated a scaled laboratory model of a blazar jet traveling through space.
To evaluate the disruption theory, the scientists directly measured the jet's beam profile and associated magnetic field signatures, revealing unexpected stability. The pair beam remained narrow and almost parallel, showing minimal disruption or evidence of self-generated magnetic fields.
When scaled to cosmic distances, this stability suggests that beam-plasma instabilities are insufficient to explain the absence of GeV gamma rays. Consequently, the outcome supports the competing hypothesis: a relic intergalactic magnetic field consistently deflects particle pairs, causing the GeV emission to elude Earth.
Professor Bob Bingham, a co-investigator from the STFC Central Laser Facility and the University of Strathclyde, emphasized the significance of these experiments in advancing our understanding of the high-energy universe. By replicating relativistic plasma conditions in the lab, scientists can measure processes shaping the evolution of cosmic jets and gain insights into the origin of magnetic fields in intergalactic space.
Despite resolving one mystery, the findings introduce a new puzzle: if the intergalactic medium possesses a magnetic field, how could it have been generated in the uniform early universe? The researchers hint that the answer may lie in new physics beyond the Standard Model.
Facilities like the upcoming Cherenkov Telescope Array Observatory (CTAO) will provide higher-resolution data to test these ideas and further unravel the secrets of the magnetic cosmos. The study's publication in the journal PNAS on November 3 marks a pivotal step in our quest to comprehend the universe's hidden magnets.
