Knots in the Helix Nebula found in H2
M. Matsuura (NAOJ, UCL), A.K. Speck (Missouri), B.M. McHunu, (Missouri), I. Tanaka (NAOJ), N.J. Wright (UCL), M.D. Smith (Kent), A.A., Zijlstra (Manchester), S. Viti (UCL), R. Wesson (UCL)

TL;DR
This study provides detailed imaging of the Helix Nebula's knots in H2 emission, revealing their shapes, distribution, and possible formation mechanisms, offering new insights into the evolution of planetary nebulae.
Contribution
First detailed H2 imaging of the Helix Nebula's knots, analyzing their morphology, distribution, and implications for nebular evolution and molecular gas survival.
Findings
Knots exhibit tadpole shapes with varying tail structures.
H2 exists only within the knots, influencing surface brightness.
Inner knots are likely overrun by faster winds, affecting their morphology.
Abstract
We present a deep and wide field-of-view (4'x 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 micron H2 v=1-0 S(1) line. The excellent seeing (0.4'') at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2.2'-6.4' from the central star (CS). At the inner edge and in the inner ring (up to 4.5' fromthe CS), the knot often show a `tadpole' shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multi-peaks within a tail. In the outer ring (4.5'-6.4' from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number…
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Taxonomy
TopicsAstrophysics and Star Formation Studies · Stellar, planetary, and galactic studies · Astro and Planetary Science
