Lithium, Beryllium and Boron: Observational Constraints on Primordial Nucleosynthesis

Abstract

Here I summarize the evidence bearing on the derivation of the primordial ⁷Li abundance from observations of extremely metal deficient stars in the galactic halo (Population II). Arguments, primarily observational, but supported theoretically, are presented to show that the ⁷Li observed in warm halo subdwarfs has neither been supplemented by ⁷Li production in the early galaxy, nor significantly depleted during the lifetime of the stars themselves, and gives a good approximation to the primordial value. The absence of ⁹Be or ¹⁰B+ ¹¹B in these objects at present limits of observational accuracy tends to support the primordiality of their ⁷Li. Observing ⁹Be, and heavier nuclides in the most metal deficient stars, does offer a possible route to distinguish between standard (SBB) and inhomogeneous (IBB) primordial cosmological models.