Updated / Mis à jour : 30-11-2010



Neutrinos are particles that interact very weakly with matter. As they are emitted in the most violent phenomena in the Universe they could elucidate which of these phenomena are at the origin of the cosmic radiation that impinges continuously on the Earth’s atmosphere. Most of this radiation is composed of charged particles, protons and nuclei that are bent by the extragalactic magnetic fields, making it very difficult to determine their origin.

Although no cosmic source has been detected yet, the ANTARES sensitivity exceeds that of any previous experiment in this hemisphere of the sky. The recording of further data will allow the observation of the Universe with an unprecedented sensitivity.



With scarcely one hundred days of data-taking, the ANTARES telescope, in a configuration of only five strings, has been able to reach a sensitivity in the southern sky higher than that of any previous experiment. In the figure, the blue squares show the limits obtained by ANTARES for the cosmic neutrino flux as a function of the declination of a group of selected astrophysical sources.

A 3D view of the Antares detector
The detection of neutrinos is a tremendous challenge that can only be undertaken using huge detectors protected from the effects of this cosmic radiation. ANTARES, deployed close to the French coast near Toulon, uses the 2000 metres of water above as a natural shielding. Its construction, has taken two years, and was completed in May 2008. Its 885 “eyes”, exceptionally sensitive photodetectors, are distributed in groups of three along 12 strings of 450 metres of height, anchored to the sea bed. They provide a sensitive surface equivalent to an area of four times a soccer pitch.

Principle of detection

The eyes of ANTARES observe the dim light trail left by muons, charged particles very similar to electrons. These muons are produced in the interaction of the upgoing neutrinos with the Earth’s crust. This faint light is detected taking advantage of the darkness in the deep sea, only broken by the sporadic light emission of some bioluminiscent creatures. ANTARES observes the southern sky using the terrestrial globe as filter and target. Muons are emitted in the same direction as their parent neutrino and therefore provide the position of their source.




Author : Thierry Stolarczyk