The capture of interstellar dust: the pure Poynting-Robertson case

Ulysses and Galileo spacecraft have discovered interstellar dust particles entering the solar system. In general, particles trajectories not altered b y Lorentz forces or radiation pressure should encounter the sun on open orb its. Under Newtonian forces alone these particles return to the interstella r medium. Dissipative forces, such as Poynting-Robertson (PR) and corpuscul ar drag and non-dissipative Lorentz forces can modify open orbits to become closed. In particular, it is possible for the orbits of particles that pas s close to the sun to become closed due to PR drag. Further, solar irradiat ion will cause modification of the size of the dust particle by evaporation . The combination of these processes gives rise a class of capture orbits a nd bound orbits with evaporation. Considering only the case of pure PR drag a minimum impact parameter is derived for initial capture by Poynting-Robe rtson drag. Orbits in the solar radiation field are computed numerically ac counting for evaporation with optical and material properties for ideal int erstellar particles modeled. The properties of this kind of particle captur e are discussed for the Sun but is applicable to other stars. (C) 2001 Else vier Science Ltd. All rights reserved.