|Messier 22 in Sagittarius. Click for larger image.|
M22 is also somewhat unique in that it is one of only four of the Milky Way's numerous globular clusters known to contain a planetary nebula, the wispy gaseous cocoon of a Sun-like star as it nears the end of its time on the main sequence and starts becoming a white dwarf. It's much too small and faint to be visible in my picture, though. I have some images I took of planetary nebulae within the Milky Way that I'll post when I run out of my backlog of globular cluster images. Also when I'm done with the current run of images I plan to make a little graphic showing the relative sizes of the various globular clusters we've seen.