Globular star clusters are a symmetrical collection of ancient stars (up to a million such stars) which are bound together gravitationally. Recent estimates indicate that about 150-200 globulars exist throughtout our galaxy with only three being readily visible to the naked eye. 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.

Strange as it may sound, hundreds of extragalactic globular clusters have been identified which are within reach of amateur imaging equipment and, in some cases, for observation as well using large aperture instruments. The Andromeda Galaxy is host to approximately 500 such globular clusters whereas at least 60 globular clusters have been identified in the relatively smaller Triangulum Galaxy. Other members of the Local Group of Galaxies with globular clusters include NGC 147 and NGC 185 in Cassiopeia, NGC 205 in Andromeda and NGC 2403 in Camelopardalis.

Note: For excellent articles on globular star clusters, see Astronomy Magazine (Apr/2008: 58-61, Sep/2008: 12-13). For an extensive discussion on the importance of studying extragalactic globular clusters systems, see the article by Markus Kissler-Patig here as well as the conference proceedings publication (also by Kissler-Patig) here.