One of the world's largest sensitive telescopes, deep underground in a Canadian nickel mine, has been looking into the heart of the sun to detect ghostly particles, or neutrinos, that are released during solar nuclear reactions. Now that the array of neutrinos has at last been observed, Peter Evans examines how this feat of engineering will transform our understanding of the sun and cause researchers to reassess the standard model of particle physics. Producer Adrian Washbourne E-mail: radioscience@bbc.co.uk