THE PECULIAR SOLAR COMPOSITION AND ITS POSSIBLE RELATION TO PLANET FORMATION

We have conducted a differential elemental abundance analysis of unprecedented accuracy (0.01 dex) of the Sun relative to 11 solar twins from the Hipparcos catalog and 10 solar analogs from planet searches. We find that the Sun shows a characteristic signature with a 20% depletion of refractory elements relative to the volatile elements in comparison with the solar twins. The abundance differences correlate strongly with the condensation temperatures of the elements. This peculiarity also holds in comparisons with solar analogs known to have close-in giant planets while the majority of solar analogs found not to have such giant planets in radial velocity monitoring show the solar abundance pattern. We discuss various explanations for this peculiarity, including the possibility that the differences in abundance patterns are related to the formation of planetary systems like our own, in particular to the existence of terrestrial planets.