Coordinates: 42°48′N 6°10′E / 42.800°N 6.167°E
ANTARES is the name of a neutrino detector residing 2.5 km under the Mediterranean Sea off the coast of Toulon, France. It is designed to be used as a directional neutrino telescope to locate and observe neutrino flux from cosmic origins in the direction of the Southern Hemisphere of the Earth, a complement to the southern hemisphere neutrino detector IceCube that detects neutrinos from the North. The name comes from Astronomy with a Neutrino Telescope and Abyss environmental RESearch project; the acronym also being the name of the prominent star Antares. 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. 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. ANTARES works by its photomultiplier tubes detecting the Cherenkov radiation emitted as the muon passes through the water. The detection techniques used discriminate between the signature of "upward-going muons", a muon neutrino that has had interactions with matter below the detector (the Earth), and much higher flux of "downward atmospheric muons".