Cat's Eye Nebula - General Information

General Information

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

While the bright inner nebula is rather small—the major axis of the inner ellipse is 16.1 arcseconds, while the distance between the condensations is 24.7 arcseconds—it has an extended halo of matter that the progenitor star ejected during its red giant phase. This halo extends over a diameter of about 300 arcseconds (5 arcminutes). The cat's Eye nebula lies three thousand light-years from Earth.

Observations show that the main body of the nebula has a density of about 5,000 particles/cm³ and a temperature of about 7,000–9,000 K. The outer halo has a higher temperature of about 15,000 K and a much lower density.

The central star of NGC 6543 is an O7 + –type star, with a temperature of approximately 80,000 K. It is approximately 10,000 times as luminous as the sun, and its radius is about 0.65 times the solar value. Spectroscopic analysis shows that the star is currently losing mass in a fast stellar wind at a rate of about 3.2×10−7 solar masses per year—about 20 trillion tons per second. The velocity of this wind is about 1900 km/s. Calculations indicate that the central star currently weighs just over one solar mass, but theoretical evolutionary calculations imply that it had an initial mass of about 5 solar masses.

In 1994, Hubble first revealed NGC 6543's surprisingly intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas.