Deep in the core of most galaxies, hidden by spinning clouds of gas and dust, black holes spin like cosmic engines. These giants — some are billions of times heavier than our sun — can shoot out streams of particles that burn along thousands of light-years. A new study by Filippo Meringolo, Federico Camilloni, and Luciano Rezzolla has revealed how this breathtaking energy release happens.
The research shows that spinning black holes can power humongous particle jets not just through magnetic torque, as has been widely assumed, but also through a process known as magnetic reconnection — a cosmic short circuit releasing humongous amounts of energy.
The Hidden Power of Magnetic Reconnection
When magnetic field lines are coiled and snap shut near a black hole, they reassemble in new configurations, releasing energy that accelerates particles nearly to the speed of light. Magnetic reconnection is a common phenomenon in the sun’s corona, where it produces solar flares, but with the presence of a black hole, it occurs in much more violent circumstances.
Total number density of particles normalized to the Goldreich–Julian density n/nGJ as measured by a FIDO observer. (CREDIT: The Astrophysical Journal Letters)
The study involves a rotating, or Kerr, black hole — an object so massive its spin distorts spacetime itself. Using advanced simulations that combine Einstein’s theory of general relativity with particle physics, the researchers demonstrated how magnetic reconnection in the twisted spacetime surrounding a black hole can access rotational energy and channel it into high-energy outflows of plasma.
Goethe University Frankfurt professor Luciano Rezzolla explained that these simulations bring researchers in more direct contact with understanding “how energy is efficiently extracted from rotating black holes and channeled into jets.”
Building the Universe’s Most Complex Simulation
To mimic the behavior of charged particles near a black hole, the team developed the Frankfurt Particle-in-Cell code (FPIC), a sophisticated computer program capable of tracking millions of electrons and positrons moving under strong gravity and magnetic influences.
The computer program simulated several black holes spinning at a variety of speeds — from relatively slow rotators to ones almost as rapid as theoretically maximum. For every simulation, it tracked how magnetic field lines from the black hole bent, snapped, and re-formed as particles moved past the event horizon, the boundary from which nothing can ever escape.
These massive calculations used supercomputers in Frankfurt and Stuttgart and were done in millions of CPU hours. “Simulating these processes is relevant to the study of the complex dynamics of relativistic plasmas in curved spacetimes around compact objects,” said Dr. Claudio Meringolo, leader of the team that created the FPIC code.
Spacetime diagrams of the total number density along the equatorial plane for BHs with spin a* = 0.7 (left panel), a* = 0.9 (middle panel), and a* = 0.999 (right panel). (CREDIT: The Astrophysical Journal Letters) A Dance of Particles and Fields
In the virtual realm, electrons and positrons orbited the black hole in a ballet of high-speed motion. As the black hole spin grew stronger, magnetic reconnection grew more frequently with increasing frequency. The faster the spin, the more energy was released by the black hole.
The simulations also revealed something unusual: inside the ergosphere — the region outside a rotating black hole where spacetime itself is dragged along — certain particles gained negative energy. When that happens, the black hole essentially loses some of its own spin energy. That energy does not just go away; it is expelled as beams of charged particles, producing bright radiation that can stretch thousands of light-years into space.
This process had been predicted theoretically decades ago as the “Penrose process,” but Meringolo and collaborators demonstrated it to play out in detail through large-scale plasma simulations. Their results illustrate how magnetic reconnection acts like an electromagnetic equivalent of that process, transforming the black hole’s spin into radiated energy.
From Equations to Cosmic Jets
Most explanations of black hole jets up to now have depended on the Blandford–Znajek mechanism, which explains how magnetic fields rooted in a rotating black hole’s environment can tap into rotational energy. Alone, though, this process couldn’t account for the record-breaking brightnesses of some active galaxies.
Averaged reconnection rate R reported as a function of the spin a* and the distance from the horizon D. (CREDIT: The Astrophysical Journal Letters)
The research shows that magnetic reconnection amplifies the effect. When the black hole’s spin approaches its limit, the rate of reconnection — the speed at which magnetic energy is converted to kinetic energy — nearly doubles. In the fastest-spinning black holes, the process becomes the main driver of their record-breaking luminosity.
It is best productive when the power output grows exponentially before eventually leveling off. This advanced information accounts for why some galaxies, such as Messier 87, possess black holes that spew jets observable over intergalactic scales.
The Case of M87*: A Cosmic Example
The galaxy M87, located in the Virgo constellation, contains one of the most famous black holes ever seen — M87*, a giant that weighs over six billion suns. Scientists first spotted a bright jet coming from its center in 1918, but its source remained a mystery for decades.
With studies like Meringolo’s, scientists now realize that M87*’s fierce spin and tangled magnetic fields can catapult matter out at speeds nearly as quick as light. These jets don’t just illuminate space; they help spread energy and matter throughout galaxies, controlling how they evolve.
Filippo Camilloni, a co-author of the study, said that the findings suggest that the traditional explanation — the Blandford–Znajek mechanism — “is not the only astrophysical process able to extract the rotational energy from a black hole, but that magnetic reconnection also contributes.”
BZ luminosity PBZ normalized to the maximum value of the lowest-order (i.e., quadratic) expression PBZ0 max, as a function of the BH angular velocity (see the top horizontal axis for a mapping in terms of the BH dimensionless spin) for all of our GRPIC simulations (black filled circles) and with the associated numerical errors. (CREDIT: The Astrophysical Journal Letters)
FPIC simulations were so accurate that they captured tiny, bubble-like plasmoids — superheated plasma pockets that form and collapse near the equator of the black hole. The effect of each impact produces a radiation and particle burst, similar to small cosmic explosions.
The Case of M87*: Results
By observing what becomes of these plasmoids, the researchers were able to determine how efficiently a rotating black hole can power jets. By their estimates, highly spinning black holes, with spin parameters exceeding about 0.8, produce the highest energy outflows. Under the most severe circumstances, these black holes can emit as much as 10⁴⁶ ergs per second — the total energy output of approximately a trillion suns.
Achieving this level of precision wasn’t easy. The simulations for each tracked more than 300 million particles, requiring strong algorithms to ensure the accuracy of each time step. The scientists traded computational speed for mathematical rigor, verifying that energy was conserved even near the event horizon, where light is bent by gravity itself.
Looking Ahead: Beyond Two Dimensions
While such simulations were done in what scientists call “2.5 dimensions” — a technique of including full electromagnetic effects within a simplified geometry — the future objective will be to move toward truly three-dimensional modeling. In such simulations, turbulence and instability can reveal even more complex behaviors that shape black hole jets.
Spacetime diagrams for the average energy at infinity of positrons〈e+,∞〉(top row) and electrons〈e−,∞〉(bottom row) for the same simulations. (CREDIT: The Astrophysical Journal Letters)
The researchers also plan to study the impact of reconnection on long-term jet evolution and jet-ambient interstellar matter interactions. Future observations by Event Horizon Telescope, which can construct direct images of black hole magnetospheres, will confirm these predictions.
By combining general relativity, plasma physics, and supercomputer simulations, the team has created the first kinetic-level demonstration of magnetic reconnection occurring within a black hole’s ergosphere. Their study bridges theory and observation and provides a deeper understanding of how nature’s most energetic engines operate.
As Rezzolla said, “It is extremely exciting to understand better what happens around a black hole with advanced numerical codes, but it’s even more satisfying to describe these findings with a careful mathematical treatment.”
Practical Implications of the Research
This discovery contributes to our understanding of how black holes fashion their cosmic surroundings. By demonstrating how rotational energy is transformed into plasma and radiation, scientists can better interpret quasar, active galaxy, and gamma-ray burst signals. These finds may also enhance models of galaxy evolution and the early universe.
On a broader level, the research strengthens the link between theoretical physics and observation, as it shows how simulations can uncover processes that other than through them are not observable.
Future telescopes and space missions might use these discoveries to monitor how black holes power and regulate cosmic environments billions of light-years distant.
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