The brightest of the Milky Way''s globular clusters, & also the largest, Omega Centauri actually outshines all but 13 of Centaurus's stars. This is what gained it a Bayer designation, typically reserved for only stellar objects. NGC5139 is it's actual catalogue number, but it is much more widely known as the Greek name.
The globular is unusual in that it contains several generations of suns, rather than the typical cluster of this type which is composed of like-age stars. This gave rise to the theory that Omega is actually the core of a once-satellite galaxy of the Milky Way, which was long ago ripped to pieces by our home system. Eventually, a few million remaining stars pulled themselves back together into a tight cluster, & resigned to orbit the Milky Way at a distance, rather than come too close to it again. Our Milky Way is known to not be kind to neighbours who venture into it's personal space.
