The Dark Side of the Sun A Plea for a Next-Generation Opacity Calculation

TL;DR

The paper argues that current solar opacity models may underestimate the true opacity, especially due to iron, and suggests that improved calculations could resolve longstanding discrepancies in solar composition and helioseismology.

Contribution

It demonstrates that adjusting elemental absorption in opacity models can reconcile solar abundance analyses with helioseismic data, highlighting the need for next-generation opacity calculations.

Findings

Iron absorption contributes 7% more to opacity than models predict.

Artificial adjustments to elemental opacities can restore model-observation agreement.

Improved opacity calculations are likely to solve the solar oxygen problem.

Abstract

Is the Sun likely to have a more opaque interior than previously thought? The solar oxygen (or abundance) problem can be solved with higher interior opacities, reconciling abundance analyses based on 3D convective atmospheres with the helioseismic structure of the solar interior. This has been known for more than a decade, but last year we learned that the absorption by just iron may contribute 7\% more to the solar opacity at the bottom of the convection zone than predicted by any opacity calculation so far, and by OP05 in particular. I find that artificial changes to the absorption (calibrated against the iron experiment) by other elements in a solar mixture give an opacity increase of a shape and magnitude that can restore agreement between modern abundance analysis and helioseismology. This suggests that improved opacity calculations will solve the solar oxygen problem.