The cosmic lithium problem: an observer's perspective

TL;DR

This paper reviews the discrepancy between predicted and observed lithium abundances in old stars, discussing potential physical processes responsible for the observed depletion and highlighting the unresolved nature of this cosmic lithium problem.

Contribution

It provides an observer's perspective on the cosmic lithium problem, reviewing various stellar processes that could explain lithium depletion in old stars.

Findings

Standard BBN predicts higher lithium than observed

Multiple stellar processes may cause lithium depletion

No fully convincing explanation for lithium depletion yet

Abstract

Using the cosmological constants derived from WMAP, the standard big bang nucleosynthesis (SBBN) predicts the light elements primordial abundances for 4He, 3He, D, 6Li and 7Li. These predictions are in satisfactory agreement with the observations, except for lithium which displays in old warm dwarfs an abundance depleted by a factor of about 3. Depletions of this fragile element may be produced by several physical processes, in different stellar evolutionary phases, they will be briefly reviewed here, none of them seeming yet to reproduce the observed depletion pattern in a fully convincing way.