We present a morphological study of the planetary nebula IC 4593, based on our observations in Hα, [O III], and [S II]. From the Hα intensity map, we calculate densities and masses for constituent structures and for the nebula as a whole. We argue that the morphology of IC 4593 suggests that it is moving supersomcally through the ISM, and that the ISM shock may be thermally unstable, oscillating between adiabatic and radiative (isothermal) shock conditions. Spectroscopic observations are necessary to further explore the nature of the interaction between IC 4593 and the ISM. An improved understanding of such interactions will greatly expand the potential use of planetary nebulae to probe the ISM.
- ISM: structure
- Planetary nebulae: individual (IC 4593)