SIMBAD references

Galactic chemical evolution (GCE), solar analogues or twins, and peculiarities of the solar composition with respect to the twins are inextricably related. We examine GCE parameters from the literature and present newly derived values using a quadratic fit that gives zero for a Solar age (i.e. 4.6 Gyr). We show how the GCE parameters may be used not only to 'correct' abundances to the solar age, but to predict average relative elemental abundances as a function of age. We address the question of whether the solar abundances are depleted in refractories and enhanced in volatiles and find that the answer is sensitive to the selection of a representative standard. The best quality data sets do not support the notion that the Sun is depleted in refractories or enhanced in volatiles. A simple model allows us to estimate the amount of refractory-rich material missing from the Sun or alternately added to the average solar twin. The model gives between zero and 1.4 earth masses.