Helioseismology and Solar Abundances

TL;DR

Helioseismology provides detailed insights into the Sun's structure, revealing discrepancies caused by revised low heavy-element abundances, and current models struggle to reconcile these differences.

Contribution

This paper reviews how heavy-element abundances influence solar models and evaluates the challenges in aligning low-abundance models with helioseismic data.

Findings

Low-metallicity models require extreme physics changes to match data.

Seismic data favors higher solar heavy-element abundances.

Efforts to reconcile low-abundance models with observations have been unsuccessful.

Abstract

Helioseismology has allowed us to study the structure of the Sun in unprecedented detail. One of the triumphs of the theory of stellar evolution was that helioseismic studies had shown that the structure of solar models is very similar to that of the Sun. However, this agreement has been spoiled by recent revisions of the solar heavy-element abundances. Heavy element abundances determine the opacity of the stellar material and hence, are an important input to stellar model calculations. The models with the new, low abundances do not satisfy helioseismic constraints. We review here how heavy-element abundances affect solar models, how these models are tested with helioseismology, and the impact of the new abundances on standard solar models. We also discuss the attempts made to improve the agreement of the low-abundance models with the Sun and discuss how helioseismology is being used to determine the solar heavy-element abundance. A review of current literature shows that attempts to improve agreement between solar models with low heavy-element abundances and seismic inference have been unsuccessful so far. The low-metallicity models that have the least disagreement with seismic data require changing all input physics to stellar models beyond their acceptable ranges. Seismic determinations of the solar heavy-element abundance yield results that are consistent with the older, higher values of the solar abundance, and hence, no major changes to the inputs to solar models are required to make higher-metallicity solar models consistent with helioseismic data.