In 2023, physicists detected something that should not have existed: a single subatomic particle called a neutrino carrying an almost unimaginable amount of energy.
This particle slammed into Earth with roughly 100,000 times more energy than anything ever produced by the Large Hadron Collider, the most powerful machine humans have built.
No known object in the universe—no star, galaxy, or black hole we currently understand—should be capable of creating it.
Now, a team of physicists at University of Massachusetts Amherst thinks they may have an answer.
In a new study published in Physical Review Letters, the researchers propose that the particle could have come from the explosion of a very unusual kind of black hole—one formed not from dying stars, but from the earliest moments of the universe itself.
Most black holes form when massive stars collapse under their own gravity. These stellar black holes are enormous, stable, and long-lived.
But in the 1970s, Stephen Hawking proposed that a different type of black hole could have formed shortly after the Big Bang. These hypothetical objects, called primordial black holes, would be much smaller and lighter than the black holes we observe today.
Hawking also showed that black holes are not perfectly black. Over extremely long timescales, they can emit particles through a process now known as Hawking radiation.
For very small black holes, this radiation would slowly drain their mass. As they shrink, they heat up, radiate faster, and eventually enter a runaway process that ends in a violent explosion.
According to the UMass Amherst team, such explosions could release an enormous burst of particles, including neutrinos with extreme energies.
In fact, the researchers have previously suggested that these events might occur as often as once every decade somewhere in the observable universe—and that modern detectors could spot them.
The idea gained new urgency when the KM3NeT neutrino detector, located deep under the Mediterranean Sea, observed the record-breaking neutrino in 2023.
But there was a puzzle. Another major neutrino observatory, IceCube in Antarctica, did not detect the event and has never seen anything even close to that energy. If exploding primordial black holes are common, why don’t we see more signals?
The answer, the researchers suggest, lies in a more exotic version of primordial black holes—ones carrying what they call a “dark charge.” This dark charge would be similar to electric charge but linked to a hidden sector of physics, including a heavy, hypothetical particle sometimes described as a “dark electron.”
Black holes with this dark charge, known as quasi-extremal primordial black holes, would behave differently from simpler models. Their explosions would be rarer and more selective, potentially explaining why one detector saw the neutrino while others did not.
Even more intriguing, this idea could connect to one of the biggest mysteries in science: dark matter. Astronomers know that galaxies contain far more matter than we can see, but the nature of that missing mass remains unknown. The researchers argue that if dark-charged primordial black holes exist, they could make up much or even all of the universe’s dark matter.
If confirmed, the implications would be staggering. The detection of that single neutrino might represent the first experimental evidence of Hawking radiation, primordial black holes, new fundamental particles, and the true nature of dark matter—all at once.
What once seemed impossible may turn out to be a rare glimpse into the universe’s deepest secrets.
