Hubble Space Telescope imaging of iras 17441-2411: A case study of a bipolar nebula with a circumstellar disk

The bipolar proto-planetary nebula IRAS 17441-2411 (the "Silkworm Nebula") was observed with the Hubble Space Telescope. By fitting the observed spect ral energy distribution and the V-band image by a two-dimensional radiation transfer model, we derive the properties of the circumstellar wind and a p roposed circumstellar "disk." We suggest that bipolar structures are probab ly more common than actually observed, because objects with similar intrins ic structures may simply appear stellar because of their orientation in the sky.