Published online by Cambridge University Press: 07 August 2017
Abell 78 is one of a group of planetaries having an old, H–rich nebula surrounding a hot star which has more recently ejected highly–processed, H–deficient material. The A78 central star has O VI emission lines and a 3700 km s−1 hot wind, and is surrounded by knots of very dusty, H-deficient material. These objects are thought to have suffered a late helium shell flash which resulted in the central star (then a white dwarf) returning to the AGB and ejecting highly-processed material.