planetary nebulae have nothing to do with planets and get their names for historical reasons: the quality previous telescopes is often not sufficient to reveal details of these objects. Since they appeared in the ocular surface such as planets, they were considered initially for distant gas planet like Jupiter or Saturn. Today we know that they represent the final stage of stellar evolution: main sequence stars like our sun swell up at the end of her life to a red giant. The hydrogen storage in the center of the star is eventually exhausted, only in a surrounding shell of the still converted to helium. In essence, however, fused with good 100 million Kelvin helium to carbon and oxygen. The shell around the core swells up enormously and the traditional balance between self-gravity and radiation pressure gets out of Rowing. The helium burning in the stellar interior is very sensitive to temperature changes and if this is just a little increased, he extends even further, because the core is increased, thus the star cools and contracts again. Sufficient energy in the interior, he can throw off his sleeve in this mechanism, then the 20 to 40 km / s flies at a temperature of 10,000 K in all directions from it. This is not necessarily rejected all the same envelope, move up so that if further outbreaks of other parts of the former hydrogen envelope. The star itself is heating up here, gets hotter and hotter and more excited by the growth of the surrounding radiation Gas to glow at: The smoke is visible as a planetary nebula, remains the core of the former main sequence star as a white dwarf. For a period of up to 10,000 years ago, this fog maintained by its stellar wind. Over time, however, it subsides and the gas is invisible by recombination at some point. Planetary nebulae are therefore a temporary phenomenon, but contributes by release of chemical elements like carbon, oxygen and its role in the development of the galaxy.
On 15 February 1786 Frederick William Herschel discovered (1738-1822) in the constellation Dragon the fog, which takes its name from its appearance, especially in photographs. It looks like the eyes of a cat, so it is called today, Cat's Eye Nebula.
Recent scientific studies of the complex structure of NGC 6543 - it is the most complicated, depending on the one Planetary nebula has been observed - suggests that the stellar wind is not just one but two stars, an O-type hyper-giant with a surface temperature of 80,000 Kelvin and an unknown companion, is responsible. This was however not yet been discovered, especially the delicate shape of the nebula suggests its existence. Many astronomers can explain the appearance of NGC 6543 only by the mutual interactions between two or more suns. The mass loss rate of the main star is massive 20 trillion tons per second, 3.2 x10 -7 solar masses per year, but he is also extremely massive!
The distance of the Cat's Eye Nebula to Earth is about 3,000 light-years and with nearly 1000 years it is still a very young planetary nebula, whose shell is expanding at 19 km / s in the surrounding space into it. It removes from us at a speed of 66 km / s.
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