A remarkable prediction of Einstein’s general theory of relativity – the theory that connects space, time and gravity – is that rotating black holes have enormous amounts of energy available to tap.
For the past 50 years, scientists have been trying to invent methods to unleash this power. Nobel laureate Roger Penrose theorized that particle disintegration could draw energy from a black hole; Stephen Hawking proposed that black holes could release energy through quantum mechanical emission; while Roger Blandford and Roman Znajek proposed electromagnetic torque as one of the most important factors in extracting energy.
Now, in a study published in the journal Physical assessment DPhysicists Luca Comisso of Columbia University and Felipe Asenjo of Universidad Adolfo Ibanez in Chile have found a new way to extract energy from black holes by breaking and rejoining magnetic field lines near the event horizon, the point from which nothing, not even light , can escape the gravity of the black hole.
“Black holes are usually surrounded by a hot ‘soup’ of plasma particles that carry a magnetic field,” said Luca Comisso, researcher at Columbia University and lead author of the study.
“Our theory shows that when magnetic field lines are properly disconnected and reconnected, they can accelerate plasma particles to negative energies and extract large amounts of energy from the black hole.”
This finding could allow astronomers to better estimate black hole spin, boost black hole energy emissions and even be a source of energy for the needs of an advanced civilization, Comisso said.
Comisso and Asenjo built their theory on the premise that reconnecting magnetic fields accelerates plasma particles in two different directions. One plasma stream is pushed against the spin of the black hole, while the other is propelled in the direction of the spin and can escape the clutches of the black hole, which releases energy as the plasma swallowed up by the black hole, negative has energy.
“It’s as if someone could lose weight by eating negative calorie sweets,” said Comisso, who explained that a black hole is essentially losing energy by eating negative energy particles. “This may sound strange,” he said, “but it can happen in an area called the ergosphere, where the spacetime continuum spins so fast that every object spins in the same direction as the black hole.”
Within the ergosphere, the magnetic reconnection is so extreme that the plasma particles are accelerated to speeds approaching the speed of light.
Asenjo, professor of physics at Universidad Adolfo Ibáñez and co-author of the study, explained that the high relative velocity between captured and escaping plasma currents allows the proposed process to extract massive amounts of energy from the black hole.
“We have calculated that the plasma excitation process can achieve 150 percent efficiency, much higher than any power plant on Earth,” Asenjo said. “Achieving more than 100 percent efficiency is possible because black holes leak energy, which is given away for free to the plasma escaping from the black hole.”
The energy extraction process envisaged by Comisso and Asenjo may already be working in a large number of black holes. That may be what triggers black hole flares – powerful bursts of radiation that can be detected from Earth.
“Our increased understanding of how magnetic reconnection takes place near the black hole could be crucial to our interpretation of current and future telescope observations of black holes, such as those from the Event Horizon Telescope,” Asenjo said.
Although it sounds like science fiction, mining energy from black holes could be the answer to our future power needs.
“In thousands or millions of years, humanity can survive around a black hole without using the energy of stars,” Comisso said. “It is essentially a technological problem. When we look at physics, there is nothing to prevent it.”
The study, Magnetic Reconnection as a Mechanism for Energy Extraction from Rotating Black Holes, was funded by the Windows on the Universe initiative of the National Science Foundation, NASA, and Chile’s National Fund for Scientific and Technological Development.
Vyacheslav (Slava) Lukin, program director at NSF, said the Foundation wants to catalyze new theoretical efforts based on groundbreaking observations at facilities such as the EHT, bringing together theoretical physics and observational astronomy under one roof.
“We look forward to the possible translation of seemingly esoteric studies of black hole astrophysics into practice,” said Lukin.
“The ideas and concepts discussed in this work are really fascinating,” said Vyacheslav (Slava) Lukin, program director at the National Science Foundation. He said NSF wants to stimulate new theoretical efforts based on groundbreaking observations, bringing together theoretical physics and observational astronomy under one roof.
“We look forward to the possible translation of seemingly esoteric studies of black hole astrophysics into practice,” he added.
Black holes gain new powers when they spin fast enough
Luca Comisso and Felipe A. Asenjo. Magnetic reconnection as a mechanism for energy recovery from rotating black holes. Phys. Rev.D. DOI: 10.1103 / PhysRevD.103.023014, journals.aps.org/prd/accepted/… 304179756dd56a93a764
Provided by Columbia University
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