Importance Of The Cat's Eye Nebula

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V. The Cat’s Eye Nebula

One of the most famous nebulae is the Cat’s Eye Nebula (NGC-6543); it was discovered by William Herschel in 1786. NGC-6543 is located in the northern constellation of Draco; it appears as a blooming center with surrounding and expanding rings. The NGC-6543 has a historical importance because it was the first nebula to be studied spectroscopically by the astronomer William Huggins in 1864; this study revealed the distinctions between PNe and the other gaseous nebulae. When Huggins studied the spectrum of NGC-6543, he found that the spectrum is dominated by discontinuous lines, emission spectrum, rather than continuous like in the stellar spectrum. The first identified line was the hydrogen Balmer line (H). This discontinuous spectrum confirms Herschel’s idea that the PN gets its energy from a nearby star. Moreover, when Hubble in 1922 found a relation
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Composition
Investigating the spectrum of NGC-6543 indicates the chemical abundances in the nebula. From stoichiometry, the nebula is expected to mostly consists of hydrogen, helium, and some other heavier elements. The abundance of the elements was investigated relative to the abundance of the hydrogen. Depending on the received flux by the observatory aperture, the ratios of the abundance of the elements may differ. However, the most observed elements in the nebula’s spectrum are H, He, C, N, O, Ne, Mg, Si, S, Cl, Ar, Fe, and K (Wesson & Liu 2004); all these elements were observed in the single, double, and triple ions forms.
VIII. Summary
First, summarizing the leading stages to the formation of PN:
1- When the core of a sun-like star fuses all of its hydrogen, it starts to fuse its helium and the star evolves to the RGB in the H-R diagram.
2- When the core fuses all of the helium, the star, with a carbonic core, evolves to the AGB where it starts to expel its outer hydrogen and helium burning layers into the surroundings.
3- These expelled dust and gaseous envelope form the

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