London, July 15 : An international team has finished building the ANTARES telescope, which will search for elusive particles called neutrinos from its base 2.5 kilometres under the Mediterranean Sea for a period of five years.
According to a report in New Scientist, if all goes well, ANTARES's design might be used to build a larger version to rival the cubic-kilometre-sized IceCube Neutrino Observatory currently under construction in the ice at the South Pole.
The giant projects would complement one another, since they would each look through the Earth at different parts of the sky.
Neutrinos are fundamental particles that are produced in many natural particle accelerators, such as supernovae and the ultra-bright centres of galaxies.
Physicists also expect to see neutrinos produced by the annihilation of dark matter, a process that may occur within the Sun.
But neutrinos interact extremely weakly with matter, so they rarely collide with atoms and are therefore difficult to observe.
"So far, detectors have only been able to conclusively find neutrinos from our own Sun and from one nearby supernova, 1987A," said particle astrophysicist John Beacom of Ohio State University in Columbus, US.
Finding so-called cosmic neutrinos could tell us something about the internal dynamics of the objects that created them, said Beacom. "We want to know how the engine works in detail. That's why it's crucial to measure this emission," he added.
To find evidence of neutrinos, physicists must wait for the particles to knock into other matter. The collision produces a charged particle called a muon, which produces a flash of detectable light when it passes through something transparent, like ice or water.
The trick is to find ice or water that is relatively deep. That's because charged particles from space called cosmic rays produce neutrinos and muons when they hit the atmosphere.
Almost all of the neutrinos produced in the Earth's atmosphere travel through the planet unhindered. This makes it tricky to distinguish atmospheric neutrinos from cosmic neutrinos.
But the relatively low-energy muons produced in the atmosphere can travel only a few kilometres.
So, by building neutrino arrays like ANTARES and IceCube deep under water or ice, astronomers can make sure that most of the muons they detect were actually produced by cosmic neutrinos.
What's more, since these detectors can look down through the Earth to see the universe, using the whole planet as a shield to absorb the riffraff of particles from the atmosphere, telescopes in different hemispheres can better observe neutrinos coming from all over the sky.
"If we see a few neutrinos a year from extraterrestrial sources, we'd be very excited," said John Carr of the Centre for Particle Physics in Marseilles, France. "That would be a significant discovery," he added.