Topics in Neutrino Astrophysics

Part of the interest in neutrino astrophysics has to do with the fascinating interplay between nuclear and particle physics issues — e.g., whether neutrinos are massive and undergo flavor oscillations, whether they have detectable electromagnetic moments, etc. — and astrophysical phenomena, such as the clustering of matter on large scales, the mechanisms responsible for the synthesis of nuclei, and the evolution of stars. The three lectures here are intended to illustrate this interplay. The first lecture reviews the solar neutrino problem which, along with the atmospheric neutrino problem, provides perhaps our strongest direct evidence that new physics lurks beyond the standard model. The second has to with the implications of neutrino properties — e.g., whether neutrinos are Dirac or Majorana particles — for stellar cooling. The final lecture describes the nucleosynthesis we think accompanies a supernova explosion, and why that synthesis is a delicate probe of neutrino oscillations. These lectures as well of those from several other 1998 TASI speakers share a common subtheme: how the extraordinary technical revolution in astronomy and astrophysics has made the microphysics of the universe more relevant. It is the precise data coming from the new generation of great observatories— maps of the cosmic microwave spectrum, precision measurements of the products of big bang nucleosynthesis, measurements of the solar neutrino spectrum, Hubble Space Telescope (HST) abundance distributions from early, metalpoor stars, detection of gamma ray bursts from cosmological sources — that allow us to form the connections between observations and the underlying microphysics. This is the driving force that is making the field of nuclear and particle astrophysics of such interest to both senior physicists and new students entering the field.