A single particle, almost intangible, has challenged the limits of human knowledge. It is a Neutrino of very high energy, first captured by the new KM3net underwater detectorin the depths of the Mediterranean. Its finding not only proves that the instrument works perfectly, but also opens a new window to the most extreme and mysterious phenomena of the cosmos.
In the words of the Naoko Kurahashi Neilson Neutrinos astronomer, from the University of Drexel in Pennsylvania, “that, in itself, has been enough to start a new era in neutrinos astronomy.”
What is the “impossible” particle that crossed the earth and challenged everything we know about the universe?
The detected neutrino crossed the whole earth without flinching, like a ghost crossing a wall. Its energy was so high – about 220 Petaelectronvolts (PEV), more than 15 times that the most powerful particle accelerator in the world can produce – that His mere existence baffles the scientific community.
“It was really surprising,” says Rosa Coniglione, a researcher at the National Institute of Nuclear Physics in Italy.
And it’s not for less. Neutrinos, those particles almost without mass that rarely interact with matter, are notoriously difficult to study. “Even today, neutrinos are especially difficult to study in experiments”says Carlos Argüelles-Delgado, physicist at Harvard University. “Neutrinos are one of the most mysterious particles in the periodic table of particle physics, known as the standard model.”
Detecting such an energetic is like finding a drop in the ocean: it happens perhaps once a year per cubic kilometer of detector. And that is precisely what KM3net did from the depths of the sea. “How is it possible that a smaller detector, after such a short period of time, detects the weirdest of all, the neutrino of greater energy?” Kurahashi Neilson wonders.
KM3net is a huge neutrin telescope installed in the depths of the Mediterranean Sea, off the coast of France. There, more than two kilometers under the surface, a matrix of light sensors patiently wait patiently the faint flash that a neutrino produces when, very rarely, it clashes with a water molecule.
“When I tried to observe this event for the first time, my program failed”Remember Paschal Coyle, physicist at the Marseille Particle Physics Center. But finally, the joint analysis with the data of the Icecube observatory – another gigantic detector installed in the Antarctic ice – allowed to confirm that the event was real. And not only real: it was exceptional.
“I’ve been waiting for KM3net’s starting for a long time,” celebrates Ryan Nichol, a physicist at the University College of London. “This event shows that its detector works perfectly. You can do much more with two detectors than with one. We can measure simultaneous sources and collect data more quickly.”
The neutrino detected did not come from the sun, nor from any nearby supernova. According to data, came from the depths of the cosmos, Probably generated by an extremely energetic event: a supermassive black hole, a blazar or even some still unknown source. But its exact origin remains an enigma.
“How is the violent universe? We really don’t know it,” says Kurahashi Neilson. “It is very possible that there is a dark star or galaxy that can only be seen in neutrinos.”
The first hypothesis aimed at a possible relationship with a special type of cosmic rays called cosmogenic neutrinos – predicted for decades but never directly observed. “It’s a very exciting possibility,” says Shirley Li, particle physics from the University of California, Irvine. “This flow has been predicted [cosmogénico] forever. This must happen, but it has never been detected. ”
However, the theory does not convince all experts. For Glennys Farrar, particle physics of the University of New York, this possibility is completely ruled out. “If there are really 220 PEV, there must be an additional population [de fuentes de neutrinos]”, He says. That is, some kind of cosmic objects still unknown that are generating them.
“These additional sources could simply be more extreme versions of the sources that Icecube already detects,” says Li. “We don’t really know how a blazar works.”
The neutrino captured by km3net is more than an isolated finding. It is a new piece in a cosmic puzzle that we barely begin to understand. “A greater energy, there are fewer neutrinos,” explains Argüelles-Delgado. “Therefore, if neutrinos of greater energy are sought, it is necessary to build very large detectors, so large that they cannot be manufactured with artificial materials.”
That is why colossal instruments such as KM3net or ICECUBE are needed, which use the planet itself as a shield and a half detection. “We are 100 % sure that [los neutrinos] They have a mass, ”says Ryan Nichol. And if they will also be their own antiparticle, as stated by a hypothesis pending verifying, They could answer one of the great cosmological questions: why is the universe made of matter and not antimatter? “If neutrinos are their own antiparticle, that could explain where the entire antimatter of the primitive universe,” adds Nichol.
But, as Argüelles-de Lelgado himself recognizes, advances are not as fast as they should. “Now we only know about them in the great conferences,” he laments. “It’s hard to know what is happening, which is a pity.”
Neutrinos, those almost impossible particles are beginning to speak. Surrers of distant stars, titanic explosions and mysteries still without name travel billions of light years to run into sensors submerged in ice or sea.
Today, a single neutrino has lit alarms, analysis and scientific imagination worldwide. Because if there is something that these invisible messengers are teaching us, it is that the universe still has many secrets to reveal. And now, more than ever, we have how to listen to them.
