2003/03/03 by M. A. Guerrero, You‐Hua Chu, Y. -H. Chu +2 · 3 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/375206
10 pages, 6 figures, 1 table, to appear in the Astronomical Journal
arxiv created 2003/03/03 · openalex publication_date 2003/06/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The Owl Nebula is a triple-shell planetary nebula with the outermost shell being a faint bow-shaped halo. We have obtained deep narrowband images and high-dispersion echelle spectra in the Hα, [O III], and [N II] emission lines to determine the physical structure of each shell in the nebula. These spatiokinematic data allow us to rule out hydrodynamic models that can reproduce only the nebular morphology. Our analysis shows that the inner shell of the main nebula is slightly elongated with a bipolar cavity along its major axis, the outer nebula is a filled envelope coexpanding with the inner shell at 40 km s -1 , and the halo has been braked by the interstellar medium as the Owl Nebula moves through it. To explain the morphology and kinematics of the Owl Nebula, we suggest the following scenario for its formation and evolution. The early mass loss at the TP-AGB phase forms the halo, and the superwind at the end of the AGB phase forms the main nebula. The subsequent fast stellar wind compressed the superwind to form the inner shell and excavated an elongated cavity at the center, but this has ceased in the past. At the current old age the inner shell is backfilling the central cavity.