Cat’s Eye Nebula

The Cat’s Eye Nebula or NGC 6543, is a relatively bright planetary nebula in the northern constellation of Draco, which was discovered by William Herschel on February 15, 1786. It was notably the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins, demonstrating that planetary nebulae were gaseous and not stellar in nature. Structurally, the object has had high-resolution images by the Hubble Space Telescope revealing knots, jets, bubbles and complex arcs, being illuminated by the central hot planetary nebula nucleus (PNN).[3] It is a well-studied object that has been observed from radio to X-ray wavelengths.

NGC 6543 is a high northern declination deep-sky object and is near the apparent position of the North Ecliptic Pole. It has the combined magnitude of 8.1, with high surface brightness. Its small bright inner nebula subtends an average of 16.1 arcsec, with the outer prominent condensations about 25 arcsec.[4] Deep images reveal an extended halo about 300 arcsec or 5 arcmin across,[5] that was once ejected by the central progenitor star during its red giant phase.

Observations show the bright nebulosity has temperatures between 7000 and 9000 K, whose densities average of about 5000 particles per cubic centimetre.[6] Its outer halo has the higher temperature around 15000 K, but is of much lower density.[7] Velocity of the fast stellar wind is about 1900 km/s, where spectroscopic analysis shows the current rate of mass loss averages 3.2×10−7 solar masses per year, equivalent to twenty trillion tons per second (20 Eg/s).[6]

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