IntroductionWhat is a planetary nebula to do with a planet? Well, physically nothing. Planetary nebulae got there name, because many of them look like planets when observed through a telescope, especially a smaller one. However, no closer relationship there. Planetary nebulae are created, when a small mass star nearing the and of his life blows off his outer gas shells and the remaining core heat this gas shell with his strong radiation. As the radiation from the central white dwarf gets weaker and the expanding gas shell gets thinner the nebula becomes fainter. Images | 
