SIMBAD references

The Sun has a [Fe/H] metallicity which is larger by +0.17±0.04dex than the average metallicity of nearby stars of solar age. This result is derived from an age-metallicity relation based on the very accurate data published by Edvardsson et al. (1993A&A...275..101E) for nearby F and G dwarfs. We adopt a radial galactic gradient in metallicity of d[Fe/H]/dR=-0.09±0.02 dex/kpc, independent of the age of the stars. From the solar anomaly and this galactic gradient, we derive that the Sun has been formed at a galactocentric distance R_i,☉=6.6±0.9kpc, if we adopt R₀=8.5kpc for the present distance of the Sun from the galactic center. Hence the Sun has migrated from its birth-place in the inner part of the Galaxy outwards by 1.9 ± 0.9 kpc during its lifetime of 4.5x10⁹years. This amount is in good agreement with predictions on the diffusion of stellar orbits in space which are based on the observed relation between velocity dispersion and age of nearby stars (i.e. on the diffusion in velocity space). The accurate determination of metallicities, coupled with a galactic gradient in metallicity, allows us to investigate empirically the diffusion of stellar orbits in space, at least in galactocentric distance. A direct consequence of this diffusion, and hence a good confirmation of it, is the increase in the dispersion of metallicities of nearby stars with increasing age. From such a relation, we derive also that the initial dispersion of metallicities is rather small. This is favourable for deriving the birth-place of the Sun from its anomaly in metallicity.