Globular star clusters are a symmetrical collection of ancient stars (up to a million such stars). Recent estimates indicate that about 150 globulars exist in the Milky Way with only three being readily visible to the naked eye (the Andromeda Galaxy has been estimated to contain approximately 500 globular clusters). Since most of the globular clusters are more common in the southern hemisphere, scientists have deduced that our sun must lie away from the galactic core of the Milky Way. One of the most beautiful such globular clusters is M13 in Hercules.

Note: The globular cluster M56 in Lyra is one of the lesser known and dimmest globular clusters within the Messier catalog. With a magnitude of only 8.4 and most of the member stars being only as bright as 13th magnitude, this Messier object can be easy to overlook. With an apparent diameter of 7.1', it lies at a distance of nearly 33,000 light-years away and spans 85 light-years across. As indicated by the image below, the globular core is neither bright nor concentrated and, hence, for its classification. The cluster was discovered by Charles Messier in 1779.

As with all globular clusters, M56 is best observed using narrow-field high-power views where, for example, the white and hot member stars provide a stunning view and similar to a large collection of diamonds against the background sky. The cluster is conveniently situated between Cygnus and Lyra, for it is approximately equidistant between Albireo (β-Cyg, mag 3.07) and Sulafat (γ-Lyr, mag 3.22) and is best observed during summer when it is directly overhead around midnight. A few degrees to the immediate north lies the stunning planetary nebula M57 (NGC 6720).

Note: For an excellent article on globular clusters, see S&T (Mar/2006: 30-36) as well as the article dedicated to M13 in Astronomy Magazine (May/2007: 64-67).