At the center of the galaxy M87, located about 55 million light-years away in the constellation Virgo, lies M87*, a supermassive black hole with a mass equivalent to six and a half billion times that of our Sun. This colossal object spins at a dizzying speed, and this rotation generates cosmic phenomena of unprecedented violence. For nearly a century, astronomers have observed without understanding these jets of matter escaping from the galaxy's core, extending thousands of light-years into intergalactic space.
Formation of a plasmoid chain in the equatorial plane of a black hole, where magnetic reconnection accelerates particles to extreme energies. The gray lines represent the magnetic field.
Credit: Meringolo, Camilloni, Rezzolla (2025)
The team from Goethe University Frankfurt, led by Professor Luciano Rezzolla, developed a simulation tool called FPIC. This computer code allows modeling with unprecedented accuracy the behavior of charged particles and electromagnetic fields in the extreme environment of a rotating black hole. The calculations, which required several million hours of processing on German supercomputers, revealed that the famous Blandford-Znajek mechanism was not solely responsible for energy extraction.
The simulations highlighted a little-known physical process: magnetic reconnection. This phenomenon occurs when magnetic field lines break and abruptly reconnect, releasing enormous amounts of energy. In the black hole's equatorial plane, this activity generates chains of plasmoids - ultra-energetic plasma structures - moving at speeds close to that of light. These plasma bursts directly contribute to powering the cosmic jets.
The study published in
The Astrophysical Journal Letters demonstrates that this magnetic reconnection produces negative energy particles, a counter-intuitive concept but perfectly described by the equations of general relativity. These exotic particles play a key role in transferring energy from the black hole to its environment. This discovery opens new perspectives for understanding how active galactic nuclei reach such extraordinary luminosities and how particles are accelerated to relativistic speeds.
Relativistic jets: cosmic highways of matter and energy
Astrophysical jets are collimated flows of matter and radiation that escape from the central regions of certain celestial objects at speeds approaching that of light. First observed in 1918 in galaxy M87, these structures often extend for tens of thousands of light-years, traversing intergalactic space.
The formation of these jets requires extreme conditions found mainly around supermassive black holes and rapidly rotating neutron stars. Their energy comes from the rotation of the central object, transferred to the environment via intense magnetic fields. Particles accelerated in these jets emit synchrotron radiation, visible across all wavelengths of the electromagnetic spectrum.
These jets play a crucial role in galaxy evolution by regulating star formation and heating intergalactic gas. When a jet impacts the surrounding medium, it creates shock waves that can either compress gas to form new stars or, conversely, disperse it and prevent star formation. This regulation partly determines the size and morphology of galaxies.
Recent observations show that jets can vary considerably in intensity and direction over astronomically short timescales. This variability is explained by matter accretion processes and magnetic reconnection near the black hole's event horizon. Detailed study of these variations allows astronomers to probe the regions closest to black holes, inaccessible through direct observation.