Cat’s Eye Nebula: Definition, Size, Discovery, Composition, Visibility

The Cat’s Eye Nebula, catalogued as NGC 6543 and Caldwell 6, is a planetary nebula 3.3 ± 0.9 kilolight-years away and 0.2 light years in diameter. Discovered by William Herschel in 1786, it is among the most intricate planetary nebulae, consisting of expanding spheres of gas. Visible from Earth with a small telescope, this faint but entertaining deep-sky object sits in the extreme northern sky and measures 350 arc seconds across.

What is the Cat’s Eye Nebula?

The Cat’s Eye Nebula is a planetary nebula, known as NGC 6543 or Caldwell 6. The nebula is located in the northern constellation of Draco and serves as a visual “fossil record” of the dynamics and late evolution of a dying star. It was one of the first planetary nebulae to be discovered.

The Cat’s Eye Nebula, catalogued as NGC 6543, is a planetary nebula of high surface brightness in the constellation Draco. It is one of the most intricate nebulae ever seen, displaying a bull’s-eye pattern of eleven or more concentric rings, intricate spiral structures, jets of high-speed gas and shock-induced knots. At its centre lies a dying Wolf-Rayet star that ejected its mass in pulses at 1,500-year intervals, sculpting the nebula’s shells. Discovered by William Herschel, it was the first nebula studied by spectroscopy in 1864 and the first whose chemical composition was measured. Observations from radio to X-ray wavelengths, including Hubble Space Telescope images, reveal its full beauty and guide ongoing research into the evolution of a dying star.

How old is the Cat’s Eye Nebula?

The Cat’s Eye Nebula is estimated to be 1,000 years old. Observations suggest the star that created the nebula ejected its mass in a series of pulses at 1,500-year intervals, indicating a late evolution of a dying star.

How big is the Cat’s Eye Nebula?

The Cat’s Eye Nebula measures about 350 arc seconds in diameter. Its bright core region is estimated at about 20,000 AU, roughly 0.2 light-years across. The outer halo extends to 5.8 arcminutes, corresponding to a diameter of about 0.4 light-year at the nebula’s distance of 3,300 light-years. An enormous but extremely faint halo of gaseous material is over three light-years across, while the outer fainter envelope reaches about 3.5 light-years. These dimensions make the Cat’s Eye Nebula about 125,000 times larger than our entire Solar System.

How far is the Cat’s Eye Nebula from Earth?

The Cat’s Eye Nebula lies about three thousand light-years from Earth. The best current estimate places Cat’s Eye Nebula distance at 3300 light-years, equal to 0.89 kpc or 1001 ± 269 parsecs. That span, 3000 to 3600 light-years, locates the planetary nebula well inside our Galaxy yet far enough for its light to have travelled since the late Stone Age.

When was the Cat’s Eye Nebula discovered?

The Cat’s Eye Nebula was discovered on February 15, 1786, by William Herschel. In 1864 William Huggins observed the nebula’s spectrum, making it the first planetary nebula examined with a spectroscope.

What is the Cat’s Eye Nebula made of?

The Cat’s Eye Nebula consists mostly of hydrogen and helium. The nebula is made of several overlapping bubbles of blue gas with long streamer-like filaments wrapped tightly around them. Cat’s Eye Nebula consists of 11 or more expanding spheres of gas. The cloud of multimillion-degree gas is in the planetary nebula known as the Cat’s Eye. The infrared emission from the Cat’s Eye is generated by a variety of elements and molecules. Cat’s Eye Nebula includes gas shells, jets of high-speed gas, and unusual shock-induced knots of gas. The Cat’s Eye Nebula has an enormous but extremely faint halo of gaseous material. At the centre of the Cat’s Eye Nebula is a dying Wolf-Rayet star. Cat’s Eye Nebula’s central bright part consists of the inner elongated bubble filled with hot gas. Cat’s Eye Nebula formed from pulses of matter emitted from the central star. The Cat’s Eye Nebula’s halo likely formed of material ejected during earlier active episodes in the star’s evolution.

How hot is the Cat’s Eye Nebula?

The main body of NGC 6543 has a temperature between 7,000 and 9,000 K, while the outer halo reaches about 15,000 K. Observations at X-ray wavelengths by the Chandra X-ray Observatory revealed an extremely hot gas unit within the planetary nebula at 1.7 × 10⁶ K. The bright central star, of O7 + WR-type stellar classification, radiates at roughly 80,000 K and is about 10,000 times as luminous as the Sun.

How to find the Cat’s Eye Nebula?

To find Cat’s Eye Nebula follow the instructions given below.

• Find Cat’s Eye Nebula 7.2° west of mag. +3.1 star Altais
• Use a small telescope to observe Cat’s Eye Nebula
• Locate Cat’s Eye Nebula within a loop of Draco
• Identify Cat’s Eye Nebula in the northern constellation of Draco
• Detect Cat’s Eye Nebula with a binocular of 60-70mm aperture
• Observe Cat’s Eye Nebula visible for most part of the year from the northern hemisphere
• Employ higher-powered telescopes to reveal a blue-green disc
• Recognize NGC 6543 by the prominent straight line of five stars running roughly north-south
• Apply an O-III filter for observation with practically no increase in contrast
• Utilize an H-beta filter for observation with practically no increase in contrast

Center your finder 7.2° west of mag. +3.1 Altais, the brightest star in the compact group that forms a straight line of five stars running roughly north-south. A small telescope shows the planetary nebula as a dim patch. Higher-powered telescopes reveal a blue-green disc shining from the gases shed by a dying star.

Why is the Cat’s Eye Nebula important?

The Cat’s Eye Nebula is important because it was the first nebula to have its chemical composition measured, a landmark that placed NGC 6543 at the foundation of planetary nebula chemistry. High-resolution imaging reveals intricate spiral structures, while 1994 Hubble observations revealed gas shells, shock-induced knots of gas, and jets of high-speed gas. Together these attributes make it the archetype for studying compound morphology. The precise formation mechanism of the inner structure remains incompletely understood, so every new map and spectrum turns the object into a natural laboratory for testing models of stellar wind interaction, precessing jets, and nebular formation. San Pedro Mártir National Observatory data show movements of different layers of gas in the nebula, supplying the kinematic detail required to constrain computer simulations. Investigations of NGC 6543 continue to drive advances in our understanding of how dying stars sculpt planetary nebulae and circulate chemically enriched gas back into the Galaxy.