The morphology and kinematics of the Fine Ring Nebula, planetary nebula Sp 1, and the shaping influence of its binary central star


  • Based on the observations made with European Southern Observatory telescopes at the La Silla or Paranal Observatories under programme IDs 74.D-0373 and 55.D-0550.



We present the first detailed spatiokinematical analysis and modelling of the planetary nebula Shapley 1 (Sp 1), which is known to contain a close-binary central star system. Close-binary central stars have been identified as a likely source of shaping in planetary nebulae, but with little observational support to date.

Deep narrow-band imaging in the light of [O iii] λ5007 Å suggests the presence of a large bow shock to the west of the nebula, indicating that it is undergoing the first stages of an interaction with the interstellar medium. Further narrow-band imaging in the light of Hα+ [N ii] λ6584 Å combined with long-slit observations of the Hα emission have been used to develop a spatiokinematical model of Sp 1. The model clearly reveals Sp 1 to be a bipolar, axisymmetric structure viewed almost pole-on. The symmetry axis of the model nebula is within a few degrees of perpendicular to the orbital plane of the central binary system – strong evidence that the central close-binary system has played an important role in shaping the nebula.

Sp 1 is one of the very few nebulae to have this link, between nebular symmetry axis and binary plane, shown observationally.