Motion of dust near exterior resonances with planet

Abstract

Motion of non-spherical cosmic dust particle under the action of electromagnetic radiation and gravitational forces of central star and a planet orbiting the star is investigated. The contribution concentrates on the problem if the particle can be trapped in commensurability resonances with the planet (a particle is in resonance with a planet when the ratio of their orbital periods is the ratio of two small integers). Trapping in the circular restricted three-body problem (planetary orbit is circle) with electromagnetic radiation coming from the star is considered. The effect of radiation plays an important role as for the possible capture in exterior resonances (particle's orbital period is larger than that for the planet): particle's optical properties not only define positions of the resonances, but also the capture times and evolution of orbital elements. Results for spherical and non-spherical particles are compared: physical difference between possibilities for resonant captures for spherical and non-spherical dust particles is pointed out.We concentrate on possible trapping of the grain in commensurability resonances – mean motion exterior resonances – with planet Neptune. The orbital evolution of non-spherical dust grains of radius ≈ 2 micrometers is numerically calculated.Capture of spherical grain in a resonance is characterized by decrease of semimajor axis outside the resonance. Non-spherical grain can exhibit also an increase of semimajor axis outside the resonance. This is the first case when a physically justified force – force given by interaction between electromagnetic radiation and non-spherical dust particle – can generate such a behaviour.