Accuray of Stellar Opacities and the Solar Abundance Problem

The abundances of some of the most common elements in the Sun has been called into question by recent analysis based on new non-LTE hydrodynamic models. The new abundances of C, N, O, Ne etc. are 30-40% lower than the ’standard’ solar abundances, which were heretofore well established and supported by precise helioseismological observations. A number of recent studies have addressed the issue from different perspectives. Given the inverse relation between opacities and abundances, another possible solution has been suggested: Upward revision of stellar opacities by about 10%. But the recalculation of astrophysical opacities by The Opacity Project (OP) and the OPAL groups has led to remarkable convergence in the final results, in spite of some fundamental differences in atomic physics and plasma physics. Deviations beyond a few percent level in the Rosseland mean opacities have been ruled out. However, we discuss the accuracy of the input physics in opacities calculations, as well as detailed monochromatic (as opposed to mean) opacities, that do in fact yield large differences in radiative accelerations derived from OP and OPAL data. In addition, we note sources of "missing opacity" that might bear on the solar abundances issue.