BIRTH AND EARLY EVOLUTION OF A PLANETARY-NEBULA

The final expulsion of gas by a star as it forms a planetary nebula-th e ionized shell of gas often observed surrounding a young white dwarf- is one of the most poorly understood stages of stellar evolution(1,2). Such nebulae form extremely rapidly (about 100 years for the ionizati on) and so the formation process is inherently difficult to observe. P articularly puzzling is how a spherical star can produce a highly asym metric nebula with collimated outflows. Here we report optical observa tions of the Stingray nebula(3,4), which has become an ionized planeta ry nebula within the past few decades(5). We find that the collimated outflows are already evident, and we have identified the nebular struc ture that focuses the outflows, We have also found a companion star, r einforcing previous suspicions that binary companions play an importan t role in shaping planetary nebulae and changing the direction of succ essive outflows(6).