Abstract:
Recent work on the initial-final mass relation for low-and intermediate-mass stars and the mass distribution of the nuclei of planetary nebulae sets a lower limit on the initial mass of progenitors of PN which is substantially higher than 1 M_sun;. With such a lower limit the theoretical estimates of the deathrate of main-sequence stars would be consistent with the observed PN birthrate only if the distance scale due to Cudworth (1974) were used. A raised lower limit on the progenitor mass also helps explain the low mean distances of planetary nebulae from the galactic plane and the paucity of PN in Population II systems.
