MPI-I-2004-NWG3-001

Determining the true shape of distant astronomical objects is a challenging task, given that terrestrial observations provide only one viewpoint. For this task, bipolar planetary nebulae are interesting objects of study because of their pronounced axial symmetry. Making use of these properties, we present a technique to automatically recover the axisymmetric structure of bipolar planetary nebulae from conventional two-dimensional images. With GPU-based volume rendering driving a non-linear optimization, we estimate the nebula's local emission density as a function of its radial and axial coordinates, and we recover the orientation of the nebula relative to Earth. The optimization refines the nebula model and its orientation by minimizing the differences between the rendered image and the original astronomical image. The resulting nebula model enables realistic 3D visualizations, e.g. for educational purposes in planetarium shows.