ABSTRACT
Planetary nebulae are very inappropriately named. Diffuse nebulae, otherwise termed galactic or gaseous nebulae, are among the most beautiful objects in the sky. Photographs taken with large ground-based telescopes, as well as with the Hubble Space Telescope, bring out their vivid colours and their bizarre forms, and even when observed visually with a small telescope they are fascinating. One case of development into a planetary nebula is Henize 1357, in Ara; it is 17 000 light-years away, and has assumed the characteristic form of a planetary. The Ring Nebula looks fairly symmetrical, but other planetaries assume bizarre forms; the Helix, the Hourglass, the Egg Nebula and the complex Cat’s Eye Nebula are good examples. Most planetaries are fairly remote; the Helix Nebula in Aquarius is the closest, at 450 light-years, and with a magnitude of 6.5 it is also the brightest. There are planetary nebulae, which are highly-evolved stars which have cast off their outer layers.
