The Dynamical Future of the Mini-cluster θ1 Ori B

Recent adaptive optics observations have shown that θ¹ Ori B is a mini-cluster composed of five stars, and that it is probably bound. The dynamical stability of such a system is, however, questionable. By means of N-body integrations we conduct an exploratory study of the dynamical fate of an ensemble of systems closely resembling θ¹ Ori B in projection, with random positions and velocities in the z-direction, and with perturbations compatible with observational errors in the plane. We find that the great majority of the systems are destroyed after 100 crossing times (about 30,000 years). Even after only five crossing times, 20% of the systems dissolve, leaving behind only a tight binary. The implications of these results for the probable age of this multiple system, the fate of stars formed in small clusters, the formation of low mass runaway stars, and the properties of visual binaries are discussed.