DISCOVERY OF A HALO AROUND THE HELIX NEBULA NGC 7293 IN THE WISE ALL-SKY SURVEY

Journal Article · Fri Aug 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/755/1/53· OSTI ID:22039154

Yong, Zhang; Hsia, Chih-Hao; Kwok, Sun ^[1]

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1. Department of Physics, Faculty of Science, University of Hong Kong (Hong Kong)

We report the discovery of an extended halo ({approx}40' in diameter) around the planetary nebula NGC 7293 (the Helix Nebula) observed in the 12 {mu}m band from the Wide-field Infrared Survey Explorer all-sky survey. The mid-infrared halo has an axisymmetric structure with a sharp boundary to the northeast and a more diffuse boundary to the southwest, suggesting an interaction between the stellar wind and the interstellar medium (ISM). The symmetry axis of the halo is well aligned with that of a northeast arc, suggesting that the two structures are physically associated. We have attempted to fit the observed geometry with a model of a moving steady-state stellar wind interacting with the ISM. Possible combinations of the ISM density and the stellar velocity are derived from these fittings. The discrepancies between the model and the observations suggest that the stellar mass loss has a more complicated history, including possible time and angle dependences.

• OSTI ID: 22039154
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 755; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
AXIAL SYMMETRY
DENSITY
INFRARED SURVEYS
PLANETARY NEBULAE
STARS
STEADY-STATE CONDITIONS
STELLAR WINDS
VELOCITY