Upper limit on the eccentricity of the orbit of the parent body consistent with trapping of the nanodust particle emitted at zero relative speed at the perihelium (heliocentric distance r₀). The argument of the perihelium of the orbit is 90° in heliographic inertial coordinates, so that the initial velocity of the particle is parallel to solar equator (v_θ = 0). The solid lines are derived from the phase space model (Eqs. (19) and (20)). The symbols show the results from numerical simulations (Eq. (1)). The two sets of curves correspond to different heliolatitudes of the point of release: colatitude θ = 70° (asterisks) and 20° (diamonds), respectively. The asterisks linked by the dotted line show the result (for θ = 70°) from the simulation including the Poynting–Robertson force.