A new synthetic distance scale for planetary nebulae.

A synthetic distance scale is determined for 330 planetary nebulae for which distances and radial velocities have been determined. The distance determinations for individual planetary nebulae are discussed along with the calibration of statistical distance scales, calibration coefficients, and the calculation of mean distances for the 330 planetaries studied. The approximate total number of planetary nebulae in the Galaxy is estimated to be 48 per cu kpc, or 25,000 if the mass of the Galaxy is 150 billion solar masses. A planetary birthrate of 3 trillionth per cu pc/yr is obtained, which confirms the possibility of a relation between planetary nebulae and white dwarfs, whose birthrate is of the same order of magnitude.