Growth of a core at 5 AU from the Sun according to eq. (1), with e and i determined by an equilibrium between perturbations from nearby cores and damping due to gas drag. Migration is neglected. Here, ﹩\Sigma _{\mathrm{solid}\,}=10﹩ g cm⁻², and ﹩\Sigma _{\mathrm{gas}\,}/ \Sigma _{\mathrm{solid}\,}=90﹩. Each curve shows growth for a different r. The dotted line shows the type I migration timescale.