Raymond Davis Jr. builds, in a deep mine at Homestake, South Dakota, a solar-neutrino detector consisting of an enormous underground tank of tetrachloroethylene, designed to detect the extremely rare interactions between neutrinos coming from the Sun and the liquid's chlorine atoms. Davis publishes in 1968 the first detections of solar neutrinos, experimentally confirming for the first time that the Sun generates energy through nuclear fusion as theoretical models predict, although he systematically detects only about a third of the expected neutrinos — a discrepancy that would remain unexplained for more than thirty years until the discovery that neutrinos change type (neutrino oscillation) during their journey from the Sun. Masatoshi Koshiba, at the University of Tokyo, builds the Kamiokande detector, a much more sensitive instrument that independently confirms solar neutrinos and also detects, in 1987, neutrinos from a supernova in the Large Magellanic Cloud, the first direct detection of neutrinos from an extrasolar source other than the Sun. Riccardo Giacconi, working independently on a different branch of observational astronomy, develops satellite-borne X-ray telescopes and discovers the first cosmic X-ray sources outside the solar system in 1962, founding X-ray astronomy as an observational discipline. Together, these works open neutrino and X-ray astronomy as observational windows onto the universe complementary to traditional visible light.