The Cat’s Eye Nebula

Image credit: NASA

Cat’s Eye Nebula (NGC 6543, Caldwell 6) is a planetary nebula in the constellation Draco. Structurally, it is one of the most complex nebulae known, with high-resolution Hubble Space Telescope observations revealing remarkable structures such as knots, jets, bubbles, and vigorous arc features. In the center of the cat’s eye is a bright, hot star; About 1000 years ago, this star lost its outer envelope, producing the nebula.

It was discovered by William Herschel on February 15, 1786, and was the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins in 1864. The results of this last investigation showed for the first time that planetary nebulae consist of gases hot, but not stars.

NGC 6543 is a well-studied planetary nebula. It is relatively bright at magnitude 8.1, and it also has a high surface gloss. It is located on the right ascension 17h 58 m 33.4 s and declination + 66 ° 37’59 “. Its high declination means that it is easily observable from the northern hemisphere, where historically largest telescopes have been located. NGC 6543 is located almost exactly in the direction of the North Ecliptic Pole.

While the bright inner nebula is quite small the major axis of the inner ellipse is 16.1 arc seconds, while the distance between the condensations is 24.7 arc seconds – a halo of matter has spread that the parent star expelled during its giant red phase. This halo extends over a diameter of approximately 300 arc seconds (5 arc minutes). The Cat’s Eye Nebula is located three thousand light-years from Earth.

In 1994, Hubble first revealed the surprisingly intricate structures of NGC 6543, including concentric layers of gas, high-velocity jets of gas, and unusual shock-induced knots of gas.

The nebula was discovered by William Herschel on February 15, 1786, who compared its appearance on a planetary disk. Cat’s Eye was the first planetary nebula to be observed with a spectroscope. It was made by pioneering spectroscopist William Huggins on August 29, 1864. Huggins’s observations, which revealed that the nebula’s spectrum was discontinuous and made up of a pair of bright lines, were the first indication that planetary nebulae consist in very rarefied greenhouse. Since those first observations, NGC 6543 has been observed across the entire electromagnetic spectrum.