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An international team comes for the first time to identify the origin of a very high energy neutrino: a black hole hidden in a distant galaxy.
For a long time, astronomers who study the Universe did as vulgum pecus : they looked at the sky, with their eyes, and that's all, or almost. Astronomy has been practiced with the naked eye for millennia, before Galileo points the first telescope to the stars, four centuries ago. But Galileo, again, used his eyes, his eyes "augmented" by the amplifying magic of optics, certainly, but his eyes, just his eyes. And that lasted another two centuries, until the eye was replaced little by little by the photographic plate. This new medium, however, recorded more or less the same radiation as the eye: the so-called "visible light."
Visible? Yes, of course, since in the course of the 20th century, radiation, of exactly the same nature as light, but invisible, began to be perceptible by astronomers, radio, infrared, ultraviolet, X and gamma radiation …
Today, almost the entire electromagnetic spectrum is detected by the various telescopes of astronomers, on Earth or in space.
End of the No, there are other forms of radiation, different in nature from the electromagnetic spectrum in general, and light in particular. In 1987, for the first time in the history of astronomy, astronomers detected "other" radiation: that of neutrinos, these ghostly particles emitted at the heart of the most energetic events of the Universe, in this case , the explosion of a supernova in the Great Cloud of Magellan. An immense progress for the researchers, giving them access to the phenomenon, even before it starts to emit light …
Second great scientific techno break in 2015, when, for the first time Once, the gravitational radiation due to the fusion of two black holes was detected. Electromagnetic radiation, neutrino radiation, gravitational radiation, three forms of "celestial messages" of profoundly different nature, which allow astronomers to study the cosmos in its most diverse manifestations, from the infinitely cold to the infinitely hot. 19659003] The researchers have just republished these two techno-scientific exploits, by reopening, a second time, the window of neutrinos …
September 22, 2017 "Neutrino telescope" IceCube, a 1-cubic-kilometer ice block in the Antarctic, has detected the pbadage of a neutrino with extraordinary energy: nearly 300 TeV, or fifty times the energy of particles accelerated in the LHC
How? This 1-cubic-centimeter ice block is located 1500 meters deep, at the South Pole, in the Amundsen-Scott base. It is equipped with more than five thousand photomultipliers, intended to detect the Cherenkov effect, that is to say the bluish light generated by the interaction of a neutrino with ice. To increase the sensitivity of this extraordinary instrument, photomultipliers are oriented … down to the center of the Earth! Thus, only neutrinos that have already pbaded through the Earth without being absorbed are detected, the background noise of solar neutrinos, arriving "from above" is eliminated. We can not imagine a more efficient filter.
This weird neutrino, randomly aligned with the blazar?
Having detected the pbadage of this ultra-energy neutrino in IceCube the researchers reconstructed its trajectory and found its origin : the constellation Orion. Automatically alerted to the detection of IceCube, telescopes throughout the electromagnetic spectrum have pointed this region of the sky, and, bingo, discovered that the galaxy TXS 0506 + 056, located four billion light-years, was precisely in emitting a gigantic flow of energy in the field of electromagnetic radiation …
TXS 0506 + 056 is a "blazar" that means that at the heart of this giant galaxy is a giant black hole and active. The black hole swallows the matter around it and sends back some of its fantastic energy in a hot plasma jet directed towards the Earth. Did you say blaze? Yes, or quasar, it's the same thing, except that a blazar has its jet directed towards us, a quasar, no. In any case, it is the heart of a giant galaxy occupied by a mbadive and active black hole.
This "first" will allow astronomers and physicists to better understand the processes at the heart of the most violent phenomena of the Universe, supernovae, stellar collisions, giant black holes …
They now have to wait for a second observation, since we can not quite exclude that the galaxy and the neutrino are in the same direction … by chance. It's unlikely ; researchers estimate less than 0.1% luck, bad luck rather, a simple incidental alignment effect.
It is therefore possible today for researchers to observe different types of radiation, which they call "multi-messenger astronomy."
The next step could, why not, see the joint observation of a nearby supernova in the three types of radiation now known, or even, dream a little … with the naked eye?
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