Sunday, 9 June 2019

NGC6543: The Eye of the Cat

For many months observing the night's sky has been somewhat frustrating for me. Unstable air currents kept sweeping over Northern Italy and therefore I was compelled to use low power only. It got so bad that stars looked like little balls, rather than points and it became even hard to resolve the cores of globular clusters. Finally, over a week ago, the sky settled down and I was again able to enjoy the full capabilities of the binoscope. 

This time, I pointed it at the famous "Cat's Eye Nebula", scientifically denominated NGC6543. It's an object that brings back fond memories because it was the first of the "more awkward NGCs" I've ever observed. My first telescope was a modest 60mm refractor and straying off the obvious Messiers seemed almost impossible, especially under my hopelessly light-polluted Flemish sky. The "NGCs", apart from a few exceptions such as the Double Cluster in Perseus, were the realm of serious telescopes and I was told not to even try because deemed too difficult; prone to certain disappointment. 

Now I had this poster of a star map hanging above my bed, which was a source of infinite fascination. For hours I could stare at those stars and the various objects that were highlighted on it. And right there it was, in the constellation of Draco, the dragon: a planetary nebula named "NGC6543". It probably was the sequence of decreasing numbers that caught my attention and I simply couldn't resist. The next clear night I got the telescope out and started searching, hopping from one little star on the map to the next until I should've arrived at the right spot, high in the sky. And there it was! It was tiny, incredibly so, but it was clearly not a star. It was a very small nebula and it stood out wonderfully in the scarcely populated star field. Imagine how proud I was to have risen to the challenge and have tried the "impossible". Also my friends at the Antwerp Observatory were seriously impressed and for me it was also a very important lesson: never give up before you've even started. 

Now, thirty-five years later, this discovery's still very much a part of me and pushes me to hunt for objects that are really considered impossible for humble amateur telescopes. In the meantime, please enjoy this sketch of the Cat's Eye, made with the binoscope at 507x. Gaseous filaments are blown away by the scorching stellar wind of the dying white dwarf star from which they originated, at a speed of 1,900 km/s! X-ray observations revealed that some gaseous filaments reach temperatures of even 1.7 million degrees due to the violent interaction with this stellar wind, which has cleared out the inner bubble of the nebula. The very complex structures around it are still not well understood and may also be caused by a small and still undiscovered companion star. The central star, of which only the core is left (surface temperature 80,000°C!) is about 10,000 times as luminous as our Sun, but will soon start to fade. The overall age of the nebula is estimated at about a thousand years, still pretty young, and will completely dissipate into space within the next 10,000 to 15,000 years. 

The distance of this nebula is estimated to be more or less 3,000 light years.

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