"First light"

Computer image of the Sudbury Neutrino Observatory. The white lines indicate the support structure for the photomultiplier tubes. The Cerenkov radiation forms a circular pattern when it strikes the wall of the detector. Coloured hexagons reveal the photomultiplier tubes that have registered photons. The region with the pink centre is thought to be due to an atmospheric muon neutrino that travelled through the Earth and up through the detector. The second ring of hits is probably from a pion produced when a neutrino ejected a quark from a proton or neutron in one of the heavy water molecules.

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