The volume filling factor as a function of time and radius of the planetesimal. Left panel: an instantaneously accreted body with the terminal radius D = 10 km (R_p(t₀) = 11.9 km) and the accretion time t₀ = 1.61 Ma. Right panel: an asymptotically accreted body with the initial radius R₀ = 1.2 km, the terminal radius D = 10 km (R_p(t₀ + t_accr) = 11.9 km), the onset time of accretion t₀ = 1.61 Ma and the accretion duration t_accr = 0.5 Ma.