THE SPECTRUM OF THE PLANETARY-NEBULA NGC-6572

A detailed, high-spectral-resolution study of the spectrum of the plan etary nebula NGC 6572 is made for the optical region 365 to 1005 nm, u sing the Hamilton echelle spectrograph of Lick Observatory, and for th e ultraviolet (UV) spectral region 125 to 3 20 nm with the high-disper sion mode of the International Ultraviolet Explorer (IUE) satellite. N GC 6572 is a rather young planetary nebula, with a high surface bright ness and a seemingly relatively regular spatial structure. This nebula and especially its central star are also variable. The rich spectrum in both the optical and UV regions offers outstanding opportunities fo r diagnostic studies, abundance determinations, and even checking atom ic processes. The prominent line spectrum of permitted lines of C II, N II, 0 II etc. may arise primarily from recombination. A density-cont rast model is constructed to obtain chemical abundances by two methods and to predict isophotal contours. The metal/hydrogen ratio appears t o be smaller than in the Sun. We suggest that NGC 6572 originated from a star of about one solar mass, and that the core may have a mass of about 0.57 M.. The expansion age of the nebula appears to be about 260 0 yr.