Exocomets in the β Pictoris system

Abstract: Comets have been a source of fascination throughout the history of man. In recent years, advances in technology have opened up for the study of extrasolar objects, among them exocomets. The first exocomets were observed in the β Pictoris system almost 50 years ago and the system has been of interest ever since. Still, it is not clearly known where these bodies originate from and how they end up in their star-grazing orbits. In this work, we attempt to answer these questions through N-body simulations of the system. Firstly, the β Pictoris system was simulated with 20 thousand test particles, their position and orbital elements were tracked over an integration length of 20 million years corresponding to the age of the β Pictoris system. Test particles were tracked and many were found to collide, be ejected, or become star-grazing. The results show that there are two regions where possible planetesimal reservoirs could be sustained over the age of the system. It was seen that star-grazers form from the two stable regions at the time scale of the age of the system, which could be an explanation to where exocomets in β Pictoris come from. The majority of star-grazers were found to approach the star at highly eccentric or hyperbolic orbits. Secondly, the identified star-grazers were subjected to simulations including the non-gravitational outgassing force, similar to the one experienced by comets in our own solar system. The simulations show that the outgassing force circularizes the eccentric orbits of test particles. Finally, the mass loss rate was estimated for particles exposed to the non-gravitational force. Kilometer sized exocomets that plunge in from the outer solar system can evaporate on a timescale of a few days as they approach the star within a distance of 0.3 AU.