Nearly twenty years ago, G. D. Rochester and I organized a Discussion Meeting here on the origin of the cosmic radiation. P art of that meeting was devoted to primary gamma rays, and this meeting was followed a few years later by a meeting devoted entirely to gamma ray astronomy. At that time gamma rays represented a ‘new window on the Universe’. Now it is the turn of neutrinos to move into that slot, although it must be said that neutrino astronomy is not as far on as gamma ray astronomy was at that stage. Nevertheless, the subject has started and has already thrown up some dramatic questions, questions of interest to both astronomer and elementary particle physicist. In the more conventional astronomies, the Sun appears to be quite well behaved, and reasonably understood, with the interests of many centring on more distant and ‘dramatic’ objects, such as supernovae and extragalactic sources. With neutrinos, however, supernovae seem to be well behaved — at the superficial level, at least and based on one event — but the Sun does not. The remarkable deficit in solar neutrino flux recorded by Davis and collaborators over the past decades has been confirmed and we look forward to hearing the details of these confirmations, as well as the energy dependence of the flux and its comparison with expectation.
Antimatter in the Universe: constraints from gamma-ray astronomy
