Key Takeaways:
- NGC 6543, the Cat's Eye Nebula, is a high surface brightness planetary nebula located in the constellation Draco, discovered in 1786 and spectroscopically confirmed as gaseous in 1864.
- With an apparent magnitude of 8.1, the nebula possesses a 20 arcsecond diameter central region and a larger 5.8 arcminute outer halo, corresponding to an estimated 0.4 light-year diameter at its 3,300 light-year distance.
- Estimated to be approximately 1,000 years old, the nebula exhibits multiple stages of planetary nebula evolution, showcasing an interaction between high-speed inner gas and a slower, outer halo, forming an ionization front.
- The Cat's Eye Nebula displays a complex inner structure, the precise formation mechanism of which remains incompletely understood, though high-resolution imaging reveals intricate spiral structures.
One of the extreme northern sky’s most entertaining deep-sky objects, the Cat’s Eye Nebula in Draco (NGC 6543), is a planetary nebula with a high surface brightness. Discovered by William Herschel in 1786, it was the first planetary whose spectrum was observed, in 1864, by William Huggins. He therefore demonstrated that planetary nebulae are gaseous. Its overall magnitude is 8.1; its small, bright disk measures 20” across; and the outer halo extends to 5.8’. At its distance of 3,300 light-years, this corresponds to a diameter of about 0.4 light-year.
The Cat’s Eye is a young planetary, at perhaps 1,000 years. In part because of this, it shows the multiple stages of a planetary nebula well. The inner, higher-speed gas is slamming into the outer, slower, “belched” halo, creating an ionization front.
The Cat’s Eye has a very complex inner structure and the mechanism behind this is not yet well understood. The nebula’s structural complexity can be seen by visual observers with high magnifications on nights of steady seeing. Large telescopes reveal hints of the multiple “spiral” structure of the inner nebula, so vividly seen in images made with the Hubble Space Telescope.
