The Empirical Foundations of Nucleosynthesis

Abstract

Theories of nucleosynthesis must be based on broad empirical foundations involving experiment in nuclear physics and observation in astronomy and geophysics. Current ideas picture nucleosynthesis taking place in ordinary stars, in supermassive stars and in an early high-temperature stage of the expanding universe. A survey is presented of new experimental results on certain key reactions in the pp chain, the CNO bi-cycle, helium burning, carbon burning, and neutron production which are important in stellar nucleosynthesis. The role of the reactions 3He(α, γ)7Be and 7Be(α, γ)11C in bridging the mass gaps at atomic weights 5 and 8 in universal and supermassive star nucleosynthesis is discussed. A brief review is given of current problems in theories of nucleosynthesis arising (1) from recent observations on helium abundances in stars, (2) from correlations between the chemical composition and the age, location and kinematical motion of stars in the Galaxy. It is concluded that definitive data are now being hard won in the laboratory but that the task of laying solid empirical foundations for theories of nucleosynthesis is only just begun.

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