Today I have another globular cluster picture for you, and this one just happens to be the next in the Messier catalog: Messier 55, in Sagittarius. This globular cluster is much closer than M54, at a moderately distant 17,600 light-years. It appears almost twice as large on the sky at 19.0 arc-minutes, but is a mere third its actual size at 96 light-years in diameter. It's also a lot less compact than M54 (class XI out of XII), and really looks quite nice.
Messier 55 in Sagittarius.
Not every object in Charles Messier's catalog was discovered by him (and he gave credit where it was due), and M54 is one such object. It was discovered by an astronomer named Nicholas Louis de Lacaille from an observatory in South Africa in 1752. Messier, having heard of this discovery, tried several times to locate the cluster starting in 1764, but was stymied by its low apparent height from his location in Paris (it is located 30 degrees south of the celestial equator, which makes it rather difficult to see from mid-northerly latitudes). In fact, it wasn't until 1778 – 14 years later – that Messier was actually able to find it, after which he included it in his famous catalog of objects.
All in all, M55 is a rather nice looking cluster, if I say so myself.