Light-element abundance variations in globular clusters

TL;DR

Globular clusters exhibit star-to-star variations in light element abundances, with recent high-resolution spectroscopy supporting models of multiple stellar generations enriched by feedback from massive stars.

Contribution

This paper reviews the observational history and discusses current models explaining light-element abundance variations in globular clusters.

Findings

Evidence for multiple stellar generations in globular clusters.

High-resolution spectra reveal abundance inhomogeneities across evolutionary phases.

Favored models involve feedback from moderate- and high-mass stars.

Abstract

Star-to-star variations in abundances of the light elements carbon, nitrogen, oxygen, and sodium have been observed in stars of all evolutionary phases in all Galactic globular clusters that have been thoroughly studied. The data available for studying this phenomenon, and the hypotheses as to its origin, have both co-evolved with observing technology; once high-resolution spectra were available even for main-sequence stars in globular clusters, scenarios involving multiple closely spaced stellar generations enriched by feedback from moderate- and high-mass stars began to gain traction in the literature. This paper briefly reviews the observational history of globular cluster abundance inhomogeneities, discusses the presently favored models of their origin, and considers several aspects of this problem that require further study.