Origin and dynamics of comets and star formation

Several important consequences that would arise for the solar system's comet population if the Sun formed in an embedded star cluster are outlined. Owing to the higher stellar number density and larger tidal fields in this environment, formation of the comet cloud wold proceed differently from that envisaged in a usually assumed isolated solar nebula scenario. In particular, early planetesimal scattering by the giant planets may lead to a substantial population of free-floating intracluster comets. Furthermore, the potentially important influence the primordial binaries may have had for cometary dynamics is emphasized. Long-period binaries are likely to accelerate planetesimal growth, and short-period binaries increase the capture cross-section of intracluster comets. Some of the intracluster comets might have been captured by the Sun and remained bound to it until after the cluster dispersed. If captured comets were in stable orbits over the remaining age of the solar system, it is expected they will constitute a second class of comets in addition to the comets scattered outwards by the planets. (C) 1997 Elsevier Science Ltd.