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A collimated jet of molecular gas from a star on the asymptotic giant branch

Naturevolume 417pages829831 (2002) | Download Citation



Evolved stars of about one solar mass are in general spherically symmetric, yet the planetary nebulae that they produce in the next phase of their evolution tend not to exhibit such symmetry. Collimated ‘jets’ and outflows of material have been observed1,2,3,4,5 up to 0.3 parsec from the central stars of planetary nebulae, and precession of those jets has been proposed1 to explain the observed asymmetries. Moreover, it has recently been shown6 theoretically that magnetic fields could launch and collimate such jets. Here we report the detection of a collimated and precessing jet of molecular gas that is traced by water-vapour maser spots 500 astronomical units (au) from the star W43A in Aquila. We conclude that the jet is formed in the immediate vicinity of the star, and infer that elongated planetary nebulae are formed by jets during the short period, of less than 1,000 years, when the star makes its transition through the proto-planetary nebula phase to become a planetary nebula.

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We thank J. Nakashima and S. Deguchi for providing the information concerning SiO maser emission and infrared images of W43A. NRAO is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. H. I. was financially supported by the Research Fellowship of the Japan Society of the Promotion of Science for Young Scientist.

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Author notes

    • Hiroshi Imai

    Present address: Joint Institute for VLBI in Europe, Postbus 2, 7990 AA, Dwingeloo, The Netherlands


  1. VERA Project Office, National Astronomical Observatory, Mitaka, Tokyo, 181-8588, Japan

    • Hiroshi Imai
    •  & Tetsuo Sasao
  2. Mizusawa Astrogeodynamics Observatory, Mizusawa, Iwate, 023-0861, Japan

    • Hiroshi Imai
    •  & Kumiko Obara
  3. Department of Physics, Kagoshima University, 890-0065, Kagoshima, Japan

    • Kumiko Obara
    •  & Toshihiro Omodaka
  4. Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire, SK11 9DL, UK

    • Philip J. Diamond


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The authors declare that they have no competing financial interests.

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Correspondence to Hiroshi Imai.

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