A group of researchers confirmed Stephen Hawking’s prediction about the evaporation of black holes by Hawking radiation, although they made an important change. According to their research, the event horizon (the boundary where nothing can escape the gravitational pull of a black hole) is not as important as previously believed in the production of Hawking radiation. Rather, gravity and the curvature of spacetime play an important role in this process. This insight extends the scope of Hawking radiation to all massive matter in the universe, implying that, over a long enough time, everything in the universe could evaporate.
Research shows that Stephen Hawking was almost right about black holes being evaporated by Hawking radiation. However, the study highlights that the event horizon is not important for this radiation, and that gravity and spacetime curvature play an important role. The findings suggest that all massive objects, not just black holes, could eventually evaporate due to a similar radiation process.
New theoretical research by Michael Wondrak, Walter van Suijlekom, and Heino Falcke of Radboud University has shown that Stephen Hawking was right about black holes, although not completely. Due to Hawking radiation, black holes eventually evaporate, but the event horizon is not as important as believed. Gravity and the curvature of spacetime also cause this radiation. This means that all massive objects in the universe, such as the remnants of stars, will eventually disappear.
Using a clever combination of quantum physics and Einstein’s theory of gravity, Stephen Hawking argued that the spontaneous creation and annihilation of pairs of particles must occur near the event horizon (the point beyond which there is no escape from the gravitational force of one[{” attribute=””>black hole). A particle and its anti-particle are created very briefly from the quantum field, after which they immediately annihilate. But sometimes a particle falls into the black hole, and then the other particle can escape: Hawking radiation. According to Hawking, this would eventually result in the evaporation of black holes.
Schematic of the presented gravitational particle production mechanism in a Schwarzschild spacetime. The particle production event rate is highest at small distances, whereas the escape probability [represented by the increasing escape cone (white)] is highest at long distances. Credit: Physical Review Letters
Spiral
In this new study, researchers at Radboud University revisited this process and investigated whether or not the existence of an event horizon really matters. They combined techniques from physics, astronomy, and mathematics to examine what would happen if pairs of particles were created around black holes. The study showed that new particles can also be created beyond this horizon. Michael Wondrak: “We show that, in addition to the well-known Hawking radiation, there is also a new form of radiation.”
Everything evaporates
Van Suijlekom: “We show that far from a black hole the curvature of spacetime plays a major role in the creation of radiation. The particles are already separated there by the tidal forces of the gravitational field.” Because it was previously thought that no radiation was possible without an event horizon, this study shows that this horizon is not necessary.
Falcke: “That means that objects without an event horizon, such as the remnants of dead stars and other massive objects in the universe, also have this type of radiation. And, after a very long time, that leads to everything in the universe eventually evaporates, like black holes. This changes not only our understanding of Hawking radiation but also our view of the universe and its future.”
The study was published on June 2 in DOI: 10.1103/PhysRevLett.130.221502
Michael Wondrak is excellence fellow at Radboud University and an expert in quantum field theory. Walter van Suijlekom is a Professor of Mathematics at Radboud University and works on the mathematical formulation of physics problems. Heino Falcke is an award-winning Professor of Radio Astronomy and Astroparticle Physics at Radboud University and known for his work on predicting and making the first picture of a black hole.
