NGC 6543
The Cat's Eye Nebula - NGC 6543
The Cat’s Eye Nebula (cataloged as NGC 6543) is a planetary nebula located in the direction of the constellation Draco, Latin for the dragon. It is one of the brightest planetary nebulae with some structure seen visually through medium size amateur telescopes. Planetary Nebulae are often abbreviated PN and are emission nebulae emitting their own light. They consist of expanding shells of ionized gas being thrown off by red giant stars in the late stages of their lives. Astronomers find distances to PNs challenging to calculate due to the extreme variability of their size and brightness. The Cat’s Eye has been estimated by Hubble to be about 3300 light years away, however, other measurements indicated as far as 5300 light years. The small bright middle area is all that is visible in a telescope eyepiece and is only about 16 arc seconds across as indicated by the central circle in this image when hovering over the image. An arc second is 1/3600th of a degree. This makes the nebula between 0.25 and 0.4 light years across or about 2 trillion miles. The much fainter outer shell of material, as indicated by the large circle in this image, is about 300 arc seconds across or 5-8 light years in diameter (30-50 trillion miles). Hubble has also tried to estimate the age of the Cat’s Eye Nebula by measuring its rate of expansion at about 1/100th arc second per year. At this rate, the inner nebula may have formed as recently as 1000 years ago. In addition to the inner and outer shells mentioned, there are two more shell groupings of material. One, is inside the inner shell seen here as a very faint inner ellipse better seen in the close-up image below. Another one is in between the inner and outer shells shown here as a transition between the reddish and blueish regions with concentric shells just visible in the image below. These concentric shells began forming about 15,000 years ago at very regular intervals and stopped when the planetary formed a millennium ago. Initially, the red giant that formed this PN was about 5 solar masses (our sun is 1 solar mass). It has since thrown off about 1 solar mass in the form of the outer, middle, inner, and inner-inner shells. Many deep observations by the Hubble Space Telescope show that structurally the Cat’s Eye is an extremely complex PN. These observations reveal knots, jets, bubbles, and complex arcs, being illuminated by the central hot planetary nebula nucleus. It has also been very well-studied from across many different wavelengths. Hovering a mouse over the top image identifies two other objects: IC 4677, merely a knot in the outer shell, and NGC 6552, a fascinating barred spiral galaxy. Stats on NGC 6543 are RA 17h 58m 33s, Dec +66° 37' 59", Mag: 8.8, Size: 16" – 300”, Class 3a+2, Central Star Mag: 11.1.  
Optics: RC Optical System 20" F/8.2 (4165.6 mm Focal Length) Date: July-August, 2020
Camera: SBIG STXL-11000 with AO-X Adaptive Optics Location: Columbus, Texas
Exposure: LRGB = 510:80:80:90 minutes Imager: Kent E. Biggs

NGC 6543