A powerful particle, known as a neutrino, recently struck Earth with remarkable energy. Scientists believe it might have originated from a rare type of exploding black hole called a primordial black hole (PBH). If true, this could challenge what we know about particle physics and dark matter.
In early 2023, researchers at the KM3NeT, a large underwater detector in the Mediterranean, spotted this unusual neutrino. It’s special because it arrived with an energy level around 220 quadrillion electron volts—about 100 times more powerful than any neutrino detected before. To put this in perspective, it’s around 100,000 times stronger than anything generated in labs like CERN’s Large Hadron Collider.
Scientists were puzzled by this extraordinary event. They suspect it may have been triggered by cosmic rays that collided with Earth’s atmosphere, causing a shower of high-energy particles. However, the energy of this particular neutrino suggested it came from an extraordinary cosmic event, which we do not yet fully understand.
A new paper accepted for publication in Physical Review Letters proposes that the source was indeed an exploding PBH. These are theorized to be tiny black holes that formed shortly after the Big Bang, as suggested by physicist Stephen Hawking in the 1970s. He claimed these minuscule black holes could emit high levels of radiation, particularly as they evaporate.
Andrea Thamm, a physicist at the University of Massachusetts, stated that lighter black holes emit more radiation as they explode. This means that the powerful neutrino could be linked to a PBH “exploding” due to its extreme energy output.
Interestingly, this neutrino wasn’t detected by other observatories, like the IceCube Neutrino Observatory in Antarctica. Given that PBHs are theorized to be common in the universe, their relative silence raises questions. Some scientists theorize that less powerful neutrinos detected earlier could be signs of these explosions.
The researchers suggest that this specific type of PBH might be different due to having a “dark charge,” which makes them harder to detect. Thamm elaborated on this idea, stating that a black hole with a dark charge behaves differently from regular models. The team is intrigued by the possibilities these primordial black holes can offer in explaining various cosmic enigmas.
While the existence of quasi-extremal PBHs remains unconfirmed, the researchers express optimism about future discoveries. They predict there’s a 90% chance we will observe an explosion from a PBH by 2035, which could be groundbreaking.
Why is this exciting? If these explosions do occur, they may unleash a catalog of subatomic particles, including known ones like the Higgs boson and theorized particles like gravitons. Additionally, these events could provide vital clues about dark matter—an elusive component of the universe that includes the gravitational forces we observe. The researchers believe quasi-extremal PBHs could account for the observed dark matter.
The cosmic community is eagerly monitoring for any signs of these explosive events. As physicist Michael Baker from UMass said, such discoveries could give us a “new window on the universe” and help clarify many of the mysteries we currently face.
