Gallery: Giant Deep-Sea Detector Hunts for Elusive Particles and Glowing Bacteria
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The world's largest underwater neutrino telescope is starting to get results, as well as some bonus seismic and biological data. The telescope, called Antares (Astronomy with a Neutrino Telescope and Abyss environmental RESearch), became the first deep-sea detector for the tiny neutral particles when it was completed in 2008. Located a mile-and-a-half beneath the surface of the Mediterranean, Antares waits patiently for streaks of upward-moving light, the signature of a neutrino passing through the Earth. Pinpointing the sources of these hard-to-find particles could help resolve some of the most puzzling mysteries in physics, such as what cosmic rays are made of and what happens to stars when they explode as supernovas. But so far, the world's biggest and best neutrino telescopes have [come up empty.]( http://stag-komodo.wired.com/wiredscience/2011/04/icecube-zilch/) By looking at a different part of the sky than other neutrino telescopes, Antares may help speed the search. It's also the only neutrino telescope in the world that can detect bioluminescent bacteria and earthquakes. "We're looking for other sources, at the center of our galaxy and other galaxies," said physicist Giorgio Giacomelli of the University of Bologna in Italy, who presented the first results from Antares at a conference in Venice on April 27 . "Our main aim is to look for cosmic sources of neutrinos, and then a search for exotic particles." This gallery takes a tour of Antares' first peeks into the neutrino sky. __Above:__ Eye Sea U(nderwater) -------------------- Antares is made up of 900 of these spherical eyes, sensitive photomultipliers that pick up and amplify light. The first line of spheres was lowered into the ocean in 2006. *Image: Antares*
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Under the Sea ------------- This artist's representation shows how Antares' sensitive eyes are arranged on 12 lines tacked to the bottom of the Mediterranean. Neutrinos -- chargeless, nearly-massless particles that resist interacting with other types of matter -- are extremely difficult to detect. A neutrino produced in the center of the sun would have to travel through several light-years' thickness of lead before having a 50 percent chance of interacting with a lead atom. So instead of looking for neutrinos directly, Antares looks for the trails left by the particles as they zip through the sea. On rare occasions, a neutrino passing through the Earth will interact with the Mediterranean waters, producing a high-energy particle called a muon. The muon produces a sort of sonic boom for light, sending a cone of pale blue light known as [Cherenkov radiation](http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/cherenkov.html) ahead of it through the ocean. Antares' 900 eyes can detect this faint muon glow. Computers back on shore help reconstruct exactly where the muon came from. *Image: Antares*
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Complementary Scopes -------------------- To avoid picking up spurious signals from Earth's atmosphere, Antares focuses on particles from the other side of the globe. Light trails moving downward through the water could have come from anywhere, but an upward-moving light trail was probably triggered by a neutrino that passed through the entire planet. This strategy gives Antares a good view of the part of the galaxy visible from the Southern Hemisphere, including the galactic center (above). Other neutrino telescopes, including the massive [IceCube]( http://stag-komodo.wired.com/wiredscience/2010/12/icecube-neutrino-antarctica/) detector at the South Pole, use a similar strategy, but see a different part of the sky (below). Another detector located half-a-mile below the surface of [Lake Baikal](http://baikalweb.jinr.ru/) in Russia sees a slightly different slice of the sky. "In this sense, one is complementary to the other," Giacomelli said. *Images: arXiv/Giacomelli 2011* [](http://stag-komodo.wired.com/wiredscience/?attachment_id=60897)
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Glowing Sea Life ---------------- Antares' globular eyes also pick up light from [bioluminescent creatures](http://stag-komodo.wired.com/wiredscience/2011/01/bioluminescent-sea-creatures/) at the bottom of the ocean. This glow is noise to the particle physicists waiting for signs of neutrinos, but valuable data for marine biologists working with the Antares team. "There's a group working with us who want to know about these bacteria, and how they move with the sea currents," Giacomelli said. Already, the detector has found some correlations between the light from bacteria and the direction of the sea currents. *Image: [catalano82](http://www.flickr.com/people/95165469@N00)/Flickr*
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Earthquakes ----------- Antares is also equipped with seismometers to keep track of how the Earth moves beneath the detectors. Each line of photomultipliers is held in place by a buoy, but that buoy can sway in the ocean currents. To keep track of the detectors' positions to within 10 cm at all times, Antares scientists need to know what forces are shaking the buoys. The seismometer system got an unexpected test in March. "We were taking data when the terrible Japanese earthquake was going on," Giacomelli said. Even though it was half-a-world away, the earthquake clearly showed up in their data. "In a certain sense our seismometer was calibrated." *Images: Antares* [](http://stag-komodo.wired.com/wiredscience/?attachment_id=60898)
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Still Searching --------------- So far, neither Antares nor IceCube has seen any definite signs of cosmic neutrinos. Most of the signals Antares has picked up in the last two years came from the atmosphere. The map (below) of all the up-going neutrino candidates that Antares has caught so far shows a sky fairly evenly peppered with possible neutrinos. But the Antares researchers are waiting for clusters of points before they can declare they've found a source. "What we will see from a cosmic source plotted in this map is not one point here, one point there," Giacomelli said. "We are looking for points that concentrate in a small blob. This will be an indication that you found something." *Images: 1) Antares. 2) arXiv/Giacomelli 2011.* [](http://stag-komodo.wired.com/wiredscience/?attachment_id=60899)
