Jupiter's moon of Io was the first other planet or moon in the universe to be shown exhibiting volcanic activity other than Earth. The picture was taken by the Galileo spacecraft. The activity, called the Prometheus Plume, has been active every time a flyby of Io has been done, including the Voyager flyby some 18 years prior, making it likely that the plume has been continuously active for over twenty years. The image has been digitally sharpened, and was taken at the distance of 600,000 miles

Links

http://en.wikipedia.org/wiki/Planetary_nebula
http://en.wikipedia.org/wiki/Cat
http://en.wikipedia.org/wiki/Dumbbell_Nebula
http://chandra.harvard.edu/photo/2001/1220/index.html
http://en.wikipedia.org/wiki/List_of_planetary_nebulae
http://en.wikipedia.org/wiki/Little_Ghost_Nebula
http://en.wikipedia.org/wiki/Hourglass_Nebula
http://www.noao.edu/jacoby/
http://zebu.uoregon.edu/~imamura/208/feb22/feb22.html
http://ad.usno.navy.mil/pne/gallery.html
http://www.astro.rug.nl/~pns/
http://www.astro.washington.edu/balick/
http://www.daviddarling.info/encyclopedia/P/planneb.html
http://stsdas.stsci.edu/elcat/

Thor's Helmet is an emission nebula. NG 2359 is about 30 light-years across. At the center of the nebula is an extremely-hot star whose formation is blowing the particles out to form what is either the helmet of a norse god or apparently a duck. The complexity of the shape is thought to originate from the nebula's interaction with other neaby astronomical bodies.