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Solar Abundances: Model Atmospheres, Line Formation and Other Obstacles Martin Asplund Abstract I will review our current knowledge of the chemical composition of the Sun as measured by spectroscopy of photospheric lines. The emphasis will be on the lighter elements (<Fe-peak). For elements not depleted in the photosphere or in the CI chondritic meteorites, the agreement between the two is good in general with some notable exceptions. I will highlight the uncertainties attached to the employed photospheric analysis regarding the solar model atmosphere and the line formation process. Using a realistic 3D, hydrodynamical simulation of the solar surface convection and accounting for departures from LTE for crucial lines, we have recently revised the solar C, N and O abundances significantly. The agreement between atomic and molecular lines is excellent, in contrast to what is achieved with 1D models. Some implications of these changes, for example helioseismology and opacity calculations, will be mentioned. |