A COMPARISON OF HIPPARCOS PARALLAXES WITH PLANETARY-NEBULAE SPECTROSCOPIC DISTANCES

The Hipparcos satellite has measured the parallax of a small sample of planetary nebulae. In this paper we consider the results for 3 planet ary nebulae (PN) for which spectroscopic distances have also been dete rmined from stellar gravities. These gravities in turn have been deriv ed from profile fitting of selected hydrogen and helium lines (Mendez et al., 1988 a, b, 1992). A comparison of these distances shows that t he Hipparcos distances are all considerably smaller. This same effect has been found in two other PN central stars, whose distance has been determined from the VLA measured nebular expansion. The question of th e mass of the central star of PHL 932 is also discussed.