ISM-induced erosion and gas-dynamical drag in the Oort Cloud

Abstract

We examine the physical interactions between material in the Oort Cloud and the interstellar medium (ISM). The model employed here accounts for sputtering, sticking, and grain-impact erosion, as well as gas drag. The model represents the ISM as a multiphase medium with two cloud-phase regimes (atomic and molecular) and two gas-phase regimes (coronal and warm/ambient). The effects of both supernova remnants and stellar winds on the Oort Cloud are also evaluated. It is found that erosion is the dominant ISM interaction. Owing to the spatial inhomogeneities in the ISM, the erosion rate is highly time variable, with essentially all erosion taking place during brief encounters with atomic and molecular clouds. Depending on the actual mechanical and surface roughness properties of cometary surfaces, 60–600 g cm −2 of material may have been lost from each comet or smaller object. ISM drag effects were found to efficiently remove submicron particles from the Cloud. Either by direct ejection or through drag forces, eroded debris particles will be lost from the Oort Cloud to the ISM. Erosion reduces the effectiveness of the thermal and radiation damage processes acting on cometary surfaces in the Oort Cloud.