Interstellar planetesimals – I. Dissipation of a primordial cloud of comets by tidal encounters with massive nebulae

Abstract

The Oort cometary cloud is subject to tidal disruption during close encounters with massive nebulae. The process is studied by numerical integration of ∼ 33 000 comet orbits, using realistic models of the Oort cloud and the interstellar medium. It is found that the cloud is rapidly cleared of long period comets, and it is concluded that such comets are probably interstellar in origin. A capture event or tidal disturbance may have taken place ≾ a few 10⁷ yr ago.