The solar chemical composition

TL;DR

The paper addresses revisions to the solar chemical composition prompted by adopting time-dependent 3D hydrodynamical model atmospheres for line formation, moving beyond traditional 1D analyses. It details the methodology of combining 3D modelling with LTE/non-LTE considerations across atomic and molecular indicators and cross-checking against meteoritic abundances. Key findings include downward adjustments of C, N, and O abundances and a lower overall metallicity, yielding $X=0.7392$, $Y=0.2486$, $Z=0.0122$ and $Z/X=0.0165$, with $Z$ roughly halved relative to earlier compilations. While these revisions harmonize several abundance indicators and ISS-like constraints, they introduce tension with helioseismology that may require opacity enhancements or further abundance refinements, underscoring the need for broader 3D non-LTE studies and improved atomic data.

Abstract

We review our current knowledge of the solar chemical composition as determined from photospheric absorption lines. In particular we describe the recent significant revisions of the solar abundances as a result of the application of a time-dependent, 3D hydrodynamical model of the solar atmosphere instead of 1D hydrostatic models. This has decreased the metal content in the solar convection zone by almost a factor of two compared with the widely used compilation by Anders & Grevesse (1989). While resolving a number of long-standings problems, the new 3D-based element abundances also pose serious challenges, most notably for helioseismology.