Published online by Cambridge University Press: 07 August 2017
Planetary nebulae (PNe) and ring nebulae around massive stars are not just superficially similar in morphologies. For massive stars that evolve through red supergiant phase, the final fast wind would sweep up the slow red supergiant wind and form a bubble of stellar material, reminiscing the two-wind formation of a PN. Sometimes it can be really difficult to determine whether the central star of a ring nebula is a PN nucleus or a Pop I massive star. Parallel studies of PNe and ring nebulae around massive stars can greatly benefit each other.