Cat's Eye Nebula (NGC 6543)
Credits: NASA , ESA , HEIC, and The Hubble Heritage Team (STScI /AURA ); Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA)
The Cat's Eye Nebula is one of the most complicated planetary nebulae. Multiple rings (at least 9 to 11) surround the nebula, suggesting either the periodic expulsion of gas from the central star (at 1500 year intervals) or the transit of a pressure wave through the material, compacting it at periodic intervals. In addition a series of bubbles surround the central elliptical cloud and knots of material, suggestive of bipolar jets can also be seen. Perhaps the best explanation for this phenomenon is that of an accreting binary star - one of the star's may be dying, ejecting material which is perhaps being accreted by its partner with the central Cat's eye Nebula itself forming within the spheres of ejected gas about 1000 thousand years ago. An accretion disc around one of the stars could give rise to collimated stellar winds coming from the poles and such winds impacting on spherical shells of matter ejected by the red giant progenitor might go some way to explaining the structure. Estimates for the mass of the central star vary from about one solar mass to more than 5 solar masses. The rate of mass loss is estimated to be 3.2 x 10-7 solar masses / year, but may have been much higher during the red giant phase (estimated at 1.5 x 10-5 solar masses /year).
Balick, B. and preston, H.L. 1987. A wind-blown model for NGC 6543. 1987. The Astronomical J. 94(4): 958-963.
balick, B., Wilson, J. and Hajian, A.R. 2001.
NGC 6543: The Rings Around the Cat's Eye. The Astronomical Journal
Bianchi, L., Cerrato, S., & Grewing, M. 1986. Mass loss from central stars of planetary nebulae - The nucleus of NGC 6543. Astronomy and Astrophysics (ISSN 0004-6361), vol. 169, no. 1-2, Nov. 1986, p. 227-236.
Wesson, R., Liu, X.-W. 2004. Physical conditions in the planetary nebula NGC
6543 Monthly Notices of the Royal Astronomical
Society, 351(3) 1026–1042,
Article updated: 8th April 2020