The planetary nebulae Abell 30 and Abell 78 are born-again nebulae, which are believed to have undergone a very late thermal pulse, resulting in the ejection of hydrogen-poor material. Born-again PNe are a rare phenomenon, only a few are known. It is really intriguing that in all cases the expansion of the hydrogen-poor ejecta is highly asymmetrical. Here we present new HST observations of the expansion of the ejecta in Abell 30 and Abell 78, and compare them to ≈20 yrs older HST images.
展开▼
