Space and Physics
PUBLISHED
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According to our best theoretical understanding, black holes can cease to exist. They emit Hawking radiation, and as they do, they slowly evaporate. The bigger the black hole, the more slowly they evaporate; but even the smallest that we know to exist will take much longer than the age of the universe. We did not think that we would ever witness the death of a black hole, but a team argues that we could. Actually, we already did.
Researchers believe that the most energetic neutrino ever detected, called KM3-230213A, is evidence of such a death. The neutrino was 35 times more energetic than the previous record holder, and 100,000 times more energetic than the particles we collide in the Large Hadron Collider. Whatever event produced it must have been of epochal energy.
The team from the University of Massachusetts (UMass) Amherst suggests that it was the death of a primordial black hole (PBH). PBHs are hypothetical black holes that might have formed right after the Big Bang. If they exist, they might have been much smaller than regular black holes, and so they have had time to evaporate… violently.
“The lighter a black hole is, the hotter it should be and the more particles it will emit,” Andrea Thamm, co-author of the new research and assistant professor of physics at UMass Amherst, said in a statement. “As PBHs evaporate, they become ever lighter, and so hotter, emitting even more radiation in a runaway process until explosion. It’s that Hawking radiation that our telescopes can detect.”
The explosions would happen at a frequency of one every decade, and they would not only emit light but also a bunch of high-energy particles, including neutrinos. The problem is that the most energetic neutrino was seen by only one experiment, the KM3NeT. A similar one called IceCube saw nothing and didn’t even see anything close to it. To explain this lack of neutrinos, the team suggests a connection with dark matter. These black holes have a hypothetical dark charge mediated by dark electrons.
“We think that PBHs with a ‘dark charge’ – what we call quasi-extremal PBHs – are the missing link,” added co-author Joaquim Iguaz Juan, a postdoctoral researcher in physics at UMass Amherst.
“There are other, simpler models of PBHs out there,” added Michael Baker, co-author and an assistant professor of physics at UMass Amherst; “our dark-charge model is more complex, which means it may provide a more accurate model of reality. What’s so cool is to see that our model can explain this otherwise unexplainable phenomenon.”
“A PBH with a dark charge,” adds Thamm, “has unique properties and behaves in ways that are different from other, simpler PBH models. We have shown that this can provide an explanation of all of the seemingly inconsistent experimental data.”
The evidence for dark matter as a real substance is very strong, but we do not know what it is or what it is made of. If these primordial black holes existed and were intimately connected to dark matter, they themselves would be part of this invisible substance.
“If our hypothesized dark charge is true,” explained Iguaz Juan, “then we believe there could be a significant population of PBHs, which would be consistent with other astrophysical observations, and account for all the missing dark matter in the universe.”
“Observing the high-energy neutrino was an incredible event,” Baker concluded. “It gave us a new window on the universe. But we could now be on the cusp of experimentally verifying Hawking radiation, obtaining evidence for both primordial black holes and new particles beyond the Standard Model, and explaining the mystery of dark matter."
Several hypothetical ideas do not make a reality. Still, something must have created neutrino KM3-230213A.
The study is published in Physical Review Letters.
