The era of the cosmic neutrinos begins

The IceCube observatory in Antarctica has revealed for the first time high-energy neutrinos coming from outside the solar system. The study, which stems from the first two years of operation of this particular telescope incorporated into the ice, was published in Science.

Large Magellanic Cloud


Ernie is the affectionate nickname that physicists of the IceCube collaboration gave the most vigorous in the group of 28 high-energy neutrinos from deep space and discovered during an observing campaign that lasted two years, from May 2010 to the same month of 2012. Neutrinos are not uncommon, quite the opposite: every second, billions of these particles impalpable mass almost non-existent, the speed of light pierce each square centimeter of the Earth. But almost all come from the Sun or the Earth’s atmosphere.

Extremely rare are neutrinos coming from distant regions of our galaxy or beyond, but they had never been seen so clearly before this study.

“This is the first indication of very high energy neutrinos coming from outside of our solar system, with energies in excess of a million times those observed in 1987 in connection with the view of supernova in the Large Magellanic Cloud,” says Francis Halzen, director of the University of Wisconsin-Madison and scientific director of IceCube . “It’s very gratifying to finally see what we have tried to see for many years. This is the dawn of a new era in astronomy. ”

But why the cosmic neutrinos are so important for astrophysics? Because they rarely interact with matter and are insensitive to magnetic fields, scientists believe that these particles may carry valuable information on the most energetic phenomena in the Universe. “High and ultra-high energy neutrinos are generated in different situations common in astrophysics, ” says Gianfranco Brunetti, INAF- IRA, “for example, by the interaction of high-energy protons and nuclei with matter and radiation environment. They can provide us with basic information on the physics of particle acceleration, not only in supernova remnants, but also in very remote objects such as gamma-ray bursts, and clusters of galaxies in the neighborhood of black holes.” “The observations of high-energy neutrinos from astrophysical sources such powerful,” adds Massimo Della Valle, Director of INAF – Astronomical Observatory of Capodimonte, “could provide valuable information on the neutrino mass or even the mysterious dark matter.

According to some theories, some of these ultra- energy neutrinos may be produced during the decay of heavy particles of the so-called dark matter. But at the moment we are still in a preliminary stage and we must understand why some of the data that emerge from this research are different from theoretical estimates. ” The detection of cosmic neutrinos high and very high energy has been possible thanks to IceCube, a special telescope located in Antarctica, in which the visible part is literally the tip of the iceberg of what lies beneath. IceCube is the largest neutrino detector in the world.

Completed in December 2010 after seven years of work at a cost of 271 million dollars, is the result of a large international collaboration supported by the U.S. National Science Foundation. It consists of 5,160 optical sensors, divided into 86 chains embedded in a cubic kilometer of ice under the South Pole. The ice itself is a component of this observatory, where the neutrinos are detected through tiny flashes of blue light, called Cherenkov light produced when neutrinos interact with the ice. “IceCube is opening a new observational window for the study of the acceleration of high energy particles in the Universe,” says Brunetti. “The data collected from IceCube, resulting from two years of observation, have identified a number of high and ultra-high energy neutrinos of astrophysical origin, but does not allow us to identify the sources of these neutrinos.

This remarkable result demonstrates the great potential of the instrument anyway. ” The next step is then to determine where they come from cosmic neutrinos, travelling undisturbed in a straight line, they can show us the place in the galaxy in which they were produced. However, the 28 events recorded so far are too few to detect any direction. Scientists at the IceCube collaboration are convinced that over the next few years, a larger number of measurements will eventually reveal the point of origin of this intriguing phenomenon.

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