Are planetary systems coplanar?

Because planets are thought to form in flat disks of gas and dust around young stars, planetary systems should have nearly coplanar orbits. Although most planetary and protoplanetary disk systems appear to be coplanar, new observations have uncovered planetary systems with large mutual inclinations, and planet-forming disks with large misalignments between neighboring annuli. In this talk, we discuss how the dynamics of planets forming in transition disks can generate misaligned planetary and protoplanetary disk systems. Specifically, secular resonances between two planets embedded in a transition disk cavity can magnify tilts, potentially explaining the misalignments observed. We also show how a massive planet can tilt an inner disk, and how this tilt can constrain the mass of undetected planets in the disk cavity. We argue misalignments may be a signature of planetary systems borne within transition disk cavities.