A few words about telescope

ANTARES is the name of a neutrino telescope residing in the Mediterranean Sea off the coast of Toulon, France. It will observe neutrinos from the Southern Hemisphere to complement the northern hemisphere work of IceCube. The name comes from Astronomy with a Neutrino Telescope and Abyss environmental RESearch project; the acronym also being the name of a prominent star. Other neutrino telescopes designed for use in the nearby area include the Greek NESTOR telescope and the Italian NEMO telescope, which are both in early design stages.

The array contains a set of twelve separate vertical strings of photomultiplier tubes. Each one has 75 optical modules and is about 350 meters long. They are anchored at the bottom of the sea at a depth of about 2.5 km, roughly 70 meters apart from each other. Unlike traditional telescopes, ANTARES works by facing downward, into the earth. This is because the earth is nearly transparent to neutrinos but not to the atmospheric muons, which produce the most important physics background in a neutrino telescope. When neutrinos enter the southern hemisphere of the earth, they usually continue traveling directly through it. On rare occasions, a few muon neutrinos interact with the water in the Mediterranean Sea. When this happens, they produce a high energy muon. As the muon passes through the water, it emits Cherenkov radiation, which ANTARES expects to detect on the photomultiplier tubes.

In contrast to the South Pole neutrino telescopes AMANDA and IceCube, ANTARES uses water instead of ice as its Cherenkov medium. As light in water is less scattered than in ice this results in a better resolving power. On the other hand, water contains more sources of background light than ice (radioactive isotopes potassium-40 in the sea salt and bioluminescent organisms), leading to a higher energy thresholds for ANTARES with respect to IceCube and making more sophisticated background-suppression methods necessary.