The planetary nebulae of PG 1159 stars - clues to their evolutionary history
It is shown that many planetary nebulae (PN) surrounding PG 1159 stars display a bipolar morphology. The frequency of these nebulae is higher than observed in other PN samples. Implications for the evolutionary history of the PG 1159 stars are discussed. Judged from our present day knowledge of PN formation it is likely that many PG 1159 stars are the result of some sort of binary evolution.