In 2025, the most energetic particles ever detected were discovered at two neutrino detectors located in Antarctica. Now scientists say that they could have been created by the explosion of a primordial black hole relatively close to the Sun.
High-energy neutrinos
Neutrinos are elementary particles with no mass or charge. They interact very weakly with other matter, making them very difficult to observe. However, scientists have built several giant detectors for this purpose, two of which—KM3NeT and IceCube—are located in Antarctica.
In February this year, they recorded the most energetic neutrinos in history. Their energy exceeded 100 peta-electron-volts. Now, researchers at the Massachusetts Institute of Technology believe that the cause of their appearance may be the death of a primordial black hole. An article about this is published in the journal Physical Review Letters.
Primordial black holes
Black holes are usually formed as a result of the collapse of massive stars. Consequently, they cannot have a mass less than a certain value. However, physicists suggest that at the very dawn of our Universe, conditions may have allowed such objects to be born directly from fluctuations in space-time.
If this is true, then primordial black holes can have arbitrarily small masses. They would, if they didn’t evaporate. Due to Hawking radiation, every black hole loses mass. However, most of them are too massive for these losses to become noticeable in the next few hundred million years.
But for a primordial black hole, a decrease in size means that it will begin to evaporate faster and faster and eventually disappear in an explosion. And scientists believe that it is precisely this process that could have generated the incredibly energetic neutrinos observed this year.
Further calculations
Researchers calculated the number and energy of particles that a black hole should emit, taking into account its temperature and decreasing mass. According to their estimates, in the last nanosecond, as soon as a black hole becomes smaller than an atom, it should emit a final burst of particles, including about 1020 neutrinos, or approximately a sextillion particles, with energies of about 100 peta-electron-volts (around the energy observed by KM3NeT).
They used this result to calculate the number of PBH explosions that should occur in the galaxy to explain the results obtained with IceCube. They found that in our region of the Milky Way galaxy, about 1,000 primordial black holes should explode per cubic parsec per year. (A parsec is a unit of distance equal to approximately 3 light-years, which is more than 10 trillion kilometers.)
Next, they calculated the distance at which one such explosion could have occurred in the Milky Way, so that only a handful of high-energy neutrinos could reach Earth and cause the recent KM3NeT event. They found that a black hole must explode relatively close to our Solar System — at a distance approximately 2,000 times greater than the distance between Earth and our Sun.
Particles emitted as a result of such a close explosion will radiate in all directions. However, the team discovered that there is a small, 8% chance that an explosion could occur close enough to the Solar System once every 14 years for a sufficient number of ultra-high-energy neutrinos to reach Earth.
According to phys.org
