NGC6543 - CAT'S EYE NEBULA

The Cat's Eye Nebula is one of the most structurally complex planetary nebulae known, located in the constellation Draco approximately 3,300 light-years from Earth. First observed by William Herschel in 1786, it was also one of the first planetary nebulae to be studied spectroscopically, when William Huggins examined it in 1864 and demonstrated that it was composed of gas rather than unresolved stars, a groundbreaking discovery that proved nebulae could be fundamentally different from star clusters. The nebula's central star is an extremely hot white dwarf with a surface temperature exceeding 80,000 Kelvin that illuminates the surrounding shells of expelled gas. The inner structure of the Cat's Eye, revealed in exquisite detail by Hubble Space Telescope images, displays a bewildering array of concentric shells, jets, knots, and arc-like features that have challenged theoretical models of planetary nebula formation. The bright inner region spans only about 20 arcseconds across, roughly 0.2 light-years in physical extent, and shows at least 11 concentric shells or rings that may represent episodic mass-loss events from the dying star. Beyond this bright core, deep images reveal a series of faint, nearly equally spaced concentric rings extending much farther out, suggesting a history of regular pulsations in the central star's mass loss occurring roughly every 1,500 years. The jets and asymmetric features in the inner nebula may indicate the presence of a binary companion star that has influenced the geometry of the mass ejection, though this companion has not been directly detected. The Cat's Eye Nebula remains one of the most important objects for understanding the final evolutionary stages of intermediate-mass stars and the physical mechanisms that shape planetary nebulae.

The bright inner nebula spans roughly 0.2 light-years across with at least 11 concentric shells, while the outer halo extends to about 3 light-years, at a distance of approximately 3,300 light-years.