Evolution of the metallicity Z_acc of the accreted gas in units of the initial metallicity Z_proto as a function of time (left panel) and mass of the proto-Sun (right panel). Several evolutionary models of circumstellar disks that include both gas and dust are shown (see text for details). The protostar mass was calculated assuming some mass loss (e.g., due to partial photoevaporation of the circumstellar disk) except in two cases, which are represented by dashed lines.