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A high-energy neutrino struck the Earth on September 22, 2017 . He came from a galaxy in the constellation of Orion and went through the IceCube experiment, which lies at a depth of between 1.45 and 2.45Km under the crust of the South Pole.
It was 20:54 and 430 milliseconds of universal time when a blue light (which is called Cherenkov Light by the scientist who discovered it) changed the story. In a nutshell, the IceCube-170922A neutrino interacts with water and produces a muon or an electron that in turn (at these energies) generates a swarm whose electrons / positrons in the water or ice go faster than the speed of light in this medium. When this happens, this blue light is emitted above
Neutrinos are not rare particles: we are traversed by several hundreds of millions of neutrinos, which do not stop not in the Earth's atmosphere but in a very small fraction. For this reason, to be able to see them you have to use very large detectors and so water or ice are one of the winning choices. The various options, in addition to a sensational trip to the labs where the detectors are located, are described in detail in the book The Frontiers of Reality by Anil Ananthaswamy
On September 22 this was not the first time IceCube detected neutrinos. ; on average, it detects 200 per day, but most have low energy. Even the announcement of high-energy neutrino detection is unprecedented, there has been one that made headlines in 2015, and as Darren Grant (IceCube spokesperson and astrophysicist) explains. at LiveScience alarms similar to those of September 22 there were already 11, without the telescopes can locate anything. "IceCube detects neutrinos [a questo livello di energia] about once a month […] it becomes a kind of routine."
The main event of this news, however, was not like the others, it was extraordinary: for the first time it was possible to identify the 39; origin of a neutrino the so-called electromagnetic counterpart : a blazar, or an active galaxy with a supermbadive black hole at its center, which lies at 4.5 billion years- Light of Us
"There did not seem to be anything extraordinary," says Grant, "the astronomers noticed the blaze, but that did not seem like a probable source, and for us, at that time, it was a kind of neutrino, we added to the list [e proseguito] ".
But Fermi researchers issue an alert: blazar TXS 0506 + 056 explodes. The Fermi telescope had detected a gamma ray emission eight times higher than usual, it was the most brilliant blazar ever seen. We do not know exactly what, but something was causing this galaxy to emit a jet of high-energy, high-energy gamma photons. This was a probable source of ICECube-170922A
Another gamma-ray observatory, MAGIC in the Canary Islands, made follow-up observations that confirmed that the blazar was the source of the neutrino and many other observers have achieved similar results.
The news comes by telegram. Not the telegram of congratulations or condolences that we know, but an Atel (astronomical telegram online): Erik Blaufuss and Claudio Kopper of IceCube have sent the first, which you can see online on this page, the confirmation of the source is coming from Fermi. 19659002] The company involved hundreds of scientists from dozens of research laboratories around the world who enrolled in a study published later in the journal Science. Enterprise, because for years, hard work meant everything was ready for that eventuality, perfecting tools and grinding a global system to quickly understand which side of the sky the suspect was coming from, then point to the telescopes.
Artistic illustration of a supermbadive black hole in the center of a galactic blazar that emits a stream of energetic particles. Credit: DESY, Laboratory of Scientific Communication
At this point, you wonder how important it is and ultimately what it means. Dr. Michela Perst of the Department of Science and High Technology of the University of Insubria explained that " the Universe is the accelerator The most powerful particles in existence IceCubes are looking for the highest energy messengers who speak to us about the history of the birth of the universe Neutrinos travel for large spaces without interacting and when we see them, they tell us where they come from. "Particle physics applied to space observation, we can begin to study their origin, we are faced with unexpected goals, much like what happened to Galilee in 1610 ".
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Neutrino studies were not devoid of problems, in The Abnormal Neutrino Gianfranco D & # 39; Anna speaks of one of the cases the less fortunate, but we measure the difficulties and problems encountered by scientists in their work.
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