HUBBLE-SPACE-TELESCOPE V-BAND IMAGING OF THE BIPOLAR PROTOPLANETARY NEBULA IRAS-17150-3224

We report Hubble Space Telescope Wide Field Planetary Camera 2 imaging of the bipolar proto-planetary nebula IRAS 17150-3224. We find a seri es of concentric arcs superposed on the two reflection nebular lobes, similar to those observed in AFGL 2688. This suggests that periodic ma ss-loss enhancement is a common phenomenon in the asymptotic giant bra nch (AGB) phase. The near circular shape of the arcs suggests that mas s loss is spherically symmetric during the AGE phase and that the bipo lar morphology develops only after the end of the AGE phase. The possi ble evolution in morphology from proto-planetary nebulae to planetary nebulae is discussed.