Planetary Nebulae

http://en.wikipedia.org/wiki/Planetary_nebulae
http://www.noao.edu/jacoby/
http://www.noao.edu/jacoby/saturn_nebula.html
http://www.seds.org/messier/Jpg/m27.jpg
http://www.seds.org/messier/planetar.html
http://astro.nineplanets.org/twn/types.html
http://zebu.uoregon.edu/~imamura/208/feb22/feb22.html