In a recent study published in Physical Review Letters, Prof. Amos Ori from our department and our alumnus Dr. Noa Zilberman, currently a postdoctoral fellow at Princeton University, explored how quantum radiation – known as Hawking radiation – emerges when a black hole forms in the gravitational collapse of a star.
This investigation shows that the radiation starts at essentially zero magnitude near the black hole’s outer boundary (the event horizon) and gradually builds up as it travels outward.
It has long been known that black holes emit particles that transport energy across spacetime (the mentioned Hawking radiation), but the exact origin of that radiated energy remained debated. Over the decades, some of the researchers had speculated that it might be released directly from the collapsing star – which would in turn result in a sudden burst, potentially disrupting the collapse and even preventing the black hole from forming.
The new analysis, using a somewhat idealized collapse model (in four spacetime dimensions), confirms instead that the radiation emerges gradually from the region in the vicinity of the forming black hole (and not in a violent flash from the infalling matter). This finding resolves a long-standing question and corroborates the more conventional picture of Hawking radiation as a gradual, steady process that cannot interfere with black hole formation in gravitational collapse.
Read the full article here: https://doi.org/10.1103/p4bk-qg3n
(arxiv: https://arxiv.org/abs/2503.00622)
