On the Origin of the Light Elements

Abstract

By light elements I mean here all stable nuclei between hydrogen and carbon and more specifically the following isotopes : D, 3He, 4He, 6Li, 7Li, 9Be, lOB, llB. While the origin of nuclei from carbon to uranium can be plausibly accounted for in terms of stellar nucleosynthesis, this does not appear to be the case for these light nuclei. It appears that the most plausible origin is nucleosynthesis in the big bang for the lighter ones, and spallation induced by galactic cosmic rays in interstellar space for the heavier ones. The study of the origin and history of these elements appears to be a very promising endeavor : by building up the Evolutionary Abundance Curve (EAC) of each isotope (i.e. cosmic abundance versus time), we may obtain a great deal of information, not only on their nucleosynthetic processes but also on features of cosmic, galactic, stellar, and even solar system physics that may have altered their abundances or their physical states. A few results will be presented here, but, clearly, much more information of utmost astrophysical interest lies in the combined observational and theoretical studies of these elements. Each new piece of experi­ mental data, in the laboratory or in the sky, is a promise of a deeper understanding of the cosmos.