They use the Gran Canarias Telescopio (GTC) to calculate the distance to which the object that emitted the extremely energetic neutrino detected last September is thanks to the “IceCube” experiment, installed in Antarctica.
There is a type of galaxies that are called active (AGN), of which, in addition to the light of the stars that compose them, we receive radiation in all the frequencies of the spectrum (from radio waves to gamma rays, passing, of course, through the light emitted by the stars that make them up). The physical processes that take place in the nucleus of these galaxies are so extreme that they produce many other highly energetic particles, as is the case of neutrinos. These are the most abundant subatomic particles in the Universe, which are everywhere, but they are very elusive. Although they are constantly bombarding the Earth, moving as fast as light, we can not see or feel them. They are “ghost” particles because they almost never interact with matter and, nevertheless, they are fundamental to understanding the laws of nature. Detecting neutrinos requires, therefore, special instruments, such as the IceCube experiment, installed at the South Pole, which uses a huge ice cube, with a size of 1 km in length, 1 km in width and 1 km in depth, as sensor to locate these particles.
On September 22, 2017, the researchers of this particular observatory announced the detection of an extremely energetic neutrino that came from a place outside the Milky Way. The news quickly spread causing a race to identify the source responsible for this emission, which by the great energy of the detected neutrino had to be an active galaxy capable of emitting gamma rays. The FERMI satellite and the MAGIC telescope, installed at the Roque de los Muchachos Observatory (Garafía, La Palma), were the first to be activated to search for sources of this type of radiation within the region of the expected sky. They discovered that the active galaxy TXS 0506 + 056 was responsible for this emission and, for the first time, it was possible to associate the emission of extragalactic neutrinos with a known source. However, the distance to which it was located was unknown, so that it was not yet possible to deduce the luminosity of the source, nor the physical processes responsible for the emission of neutrinos.
To measure it, spectroscopic observations were necessary with “conventional” telescopes, but all attempts failed because their signal was too dim. So a team of researchers led by the astrophysicist Simona Paiano, from the Padova Observatory of the INAF (Instituto Nazionale di Astrofisica) and by Riccardo Scarpa, astronomer of the GTC, decided to observe this source with the largest optical-infrared telescope in the world. say the Gran Telescopio Canarias, on La Palma. The results have recently been published in The Astrophysical Journal.