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A circumplanetary disk is a disk surrounding a planet analogous to a circumstellar disk around a star. These are theorized and there exist candidates for such disks around known extra-solar planets. They are presumed to occur in young systems and presumed to be a significant source of moons.
Saturn's ring system can be classified as a circumplanetary disk of sorts, but the term was likely coined for disks occurring around the time of a planet's formation, i.e., when its moons generally formed. Saturn's rings are thought possibly to be leftovers from such a disk, or possibly debris from moons, broken up by impact or tidal force.