It is proposed that there are two distinct types of planetary nebulae, distinguishable observationally on the basis of Doppler expansion velocity and the difference in brightness of the nebula and its central star. The distinction extends also to the spectral types of the central stars and is related to differences found by Kaler (Astrophys. J.; l60: 887(1970)) between planetaries with differing chemical composition. (auth)

Two distinct types of planetary nebulae can be observed based on Doppler expansion velocity, nebula brightness, and central star spectral types, with the distinction also extending to differences between planetaries with differing chemical compositions.

Paper

Planetary Nebulae: Two Types

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