Context. Understanding the formation of collimated outflows is one of the most debated and controversial topics in the study of the late stages of stellar evolution.
Methods: Imaging monitoring at sub-arcsec resolution of the evolution of the nebula in the past decade is presented. Spectroscopic data provide complementary information.
Results: We determine the proper motions of the dusty blobs, which infer a new distance estimate of 1.3 ± 0.2 kpc, a total nebular size of 0.8 pc, a speed of 147 km s-1, and a kinematical age of 2500 yr. The corkscrew geometry of the inner rotating pattern is confirmed and quantified. Different recombination timescales for different ions explain the observed surface brightness distribution. According to the images taken after 1999, the pattern rotates with a period of 92 ± 4 years. On the other hand, the analysis of images taken between 1952 and 1977 measures a faster angular velocity. If the phenomenon were related to orbital motion, this would correspond to a modest orbital eccentricity (e = 0.10 ± 0.05), and a slightly shorter period (86 ± 5 years). New features have appeared after 2005 on the west side of the lobes and at the base of the pattern.
Conclusions: The geometry and travelling times of the rotating pattern support our previous proposal that the phenomenon is produced by a collimated spray of high velocity particles (jet) from the central source, which excites the walls of the inner cavity of
Astronomy and Astrophysics
- Pub Date:
- May 2011
- planetary nebulae: individual: M 2-9;
- ISM: jets and outflows;
- stars: winds;
- binaries: symbiotic;
- Astrophysics - Astrophysics of Galaxies
- Accepted for publication on Astronomy and Astrophysics (10 pages, 8 figures)