Planetary Nebulae

Abstract

As tracers of an intermediate population of stars, planetary nebulae are useful objects to detect in other galaxies. As indicators of chemical processing of stellar abundances, they are important sources of information about chemical differences within and between galaxies. Furthermore, planetary nebulae are useful for studying disk dynamics, as their emission-line spectra make it easy to obtain accurate radial velocities. They are often luminous enough to detect even in galaxies much more distant than M31, and so they have been exploited for the extragalactic distance scale, using the sample in M31 and other Local Group members as calibrators. Finally, a complete census of planetary nebulae can give a direct measure of the death rate of stars of a particular type.