Neutrinos, mysterious subatomic particles, often witnesses of unprecedented power events in the Universe.
Neutrinos are subatomic particles, they don’t have electric charge and, and for a long time they were supposed to be also free of mass. In reality experiments have shown that they have a mass about 100,000 times smaller than that of the electron. They interact little or nothing with the material, they cross us every day without leaving traces of their passage. The only forces able to influence them are the gravitational force and the weak electronuclear force.
But if neutrinos are so elusive, how can we capture them and then study them? In fact, the solution is not so easy. The cosmic neutrino detectors are very large, usually built in the subsoil to shield them from cosmic rays. Among the various types of neutrino detectors there are those based on water. An enormous underground cistern of water is crossed by neutrinos, which hit the electrons of water molecules. At each impact, a neutrino gives part of its energy to an electron that starts moving at a speed greater than what light would do in the water. An optical emission is then generated, called Čerenkov radiation, which can be detected with photomultipliers.
Another type of neutrino detector is the IceCube Neutrino Detector. Built in Antarctica, it is composed of spherical geometry sensors with inside the photomultipliers, inserted in the ice at a depth between 1,450 and 2,450 meters below the frozen surface. The concept is very similar to that of water detectors: when a neutrino hits an ice water molecule, a Čerenkov radiation is generated which is detected by the sensors. At this point, a sophisticated software is able to reconstruct the parameters of the neutrino trajectory.
The IceCube Neutrino Detector has just set a new milestone in multi-message astronomy. Immediately after detecting the neutrino, in fact, he launched an international alarm which was answered by several telescopes that immediately aimed their detectors towards the constellation of Orion. Among the telescopes that participated we mention the Fermi gamma telescope, the Agile space telescope (of Italian production) and the Magic instrument in the Canaries. All identified the gamma photons from Txs 0506+056, a known active galaxy containing within it a supermassive black hole. In this case, the neutrino would have originated from a blazar, one of the most violent phenomena in the Universe, associated with the supermassive black hole contained in the center of the galaxy Txs 0506+056, about 5 billion light years away.
This is the new frontier of astronomy: to study a celestial phenomenon on several bands of the electromagnetic spectrum, in order to obtain more information and also to have a greater chance to observe unique astronomical phenomena such as the supernovae.