Wednesday, July 26, 2006

SPACE : Relic neutrinos join the hunt for dark energy

MASSIVE optical telescopes on mountain tops have been the main tools for exploring dark energy - the mysterious stuff that is accelerating the expansion of the universe. Soon the quest could move underground. Neutrinos born in stellar cataclysms and detected in gigantic water tanks buried in mines may become the new probes for dark energy.When the core of a massive star grows too large, it collapses under its own gravity, releasing a flood of neutrinos . The millions of core-collapse supernovae that have gone off throughout the history of the universe must have created a background of supernova relic neutrinos. But the diffuse nature of these neutrinos makes them very difficult to detect. However, the next generation of neutrino detectors, such as the planned Underground Nucleon decay and Neutrino Observatory will have tanks that can hold a million tonnes of water and so should be up to the job. Relic neutrinos might merely confirm the acceleration, leaving the exact nature of dark energy a mystery - or they could reveal new physics. Neutrinos might bounce off dark energy, in which case their spectrum will be distorted in such a way as to tell us something more about this mysterious force.Or it may be that light from distant supernovae is being distorted in some strange way - perhaps by being gradually converted into particles called axions. Finally, the spectrum of supernova relic neutrinos could reveal whether anything is awry.


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