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P. Kalas (Space Telescope Science Institute), J.D. Larwood (Queen Mary and Westfield College), B.A. Smith (University of Hawaii), A. Schultz (Space Telescope Science Institute)
The nearby main sequence star beta Pic is surrounded by an edge-on disk of dust produced by the collisional erosion of larger planetesimals. We have collected deep, ground- and space-based optical images of beta Pic over a 14 year time interval in order to reliably map the circumstellar environment and test for the existence of stellar or sub-stellar companions.
The data reveal the existence of radial substructure within the northeast extension of the disk midplane that is not present in the southwest extension. We hypothesize that the midplane features represent the edge-on view of an asymmetric ring system around beta Pic. We present a dynamical model demonstrating that a close stellar flyby with a quiescient disk of planetesimals can create such rings, along with previously unexplained disk asymmetries. We therefore infer that beta Pic's circumstellar disk was highly disrupted by a stellar encounter in the last hundred thousand years. These findings demonstrate that encounters with passing stars can significantly influence the evolution and observational appearance of planetesimal systems.