The Peculiar Planetary Nebula M1-78
The question of whether Ml-78 is a PN or a compact H II region is discussed. We have obtained new high resolution radio continuum maps, optical spectra and CO maps. Arguments for it being a PN include spectral information, far infrared continuum emission, and radio morphology. It is the strongest CO emitting PN known. Its abundances are peculiar: high helium and very low oxygen and nitrogen abundances. If it is a PN it must be within 4 kpc, but 21-cm absorption measurements indicate that it may be further away.