Rings in the planetesimal disk of beta Pictoris

The nearby main-sequence star beta Pictoris is surrounded by an edge-on dis k of dust produced by the collisional erosion of larger planetesimals. Here we report the discovery of substructure within the northeast extension of the disk midplane that may represent an asymmetric ring system around beta Pie. We present a dynamical model showing that a close stellar flyby with a quiescent disk of planetesimals can create such rings, along with previous ly unexplained disk asymmetries. Thus we infer that beta Pie's planetesimal disk was highly disrupted by a stellar encounter in the last hundred thous and years.