Our Local Astrophysical Laboratory

摘要

Saturn's elegant lings (see the figure, top and inset) embody all that is wondrous and exotic about the universe (1). Planetary rings are surely beautiful, but they also provide astronomers with nearby—albeit imperfect— analogs (2) for the very remote, massive proto-planetary disks (see the figure, bottom left) that surround many young stars and form the nurseries of extrasolar planets (3). Although the events deep within protoplanetaiy disks are obscured by dust and can only be inferred, ongoing observations of the Saturn system by the capable Cassini spacecraft (1) let us view—in real time—the complex dynamics that operate in our neighborhood's astrophysical disk. As described below, some of the processes that Cassini has observed address questions relevant to the solar system's origin: how hordes of orbiting bodies crowd together, how material accumulates in such systems to form moons or planets, and how nearby masses disturb—and are perturbed by—adjacent disks.