Omega Centauri is the single largest globular cluster orbiting the Milky Way galaxy. At an estimated 10 million stars it is about ten times larger than the next largest. It is so large in fact that many astronomers believe it is the core of a disrupted dwarf galaxy. It is believed to even have a central black hole like any self respecting galaxy would. Also, the spectra of stars within it show much more variety than is typical for a globular cluster.
Omega Centauri has been my favorite globular cluster since I was a toddler, long before anyone suspected it had extra-galactic origins. My favorite, in part because it is so hard to observe from Arkansas where it never ventures more than 7 degrees above the horizon. That is the width of four fingers held at arm’s length. Last night, at the River Ridge Observatory, my telescope was almost horizontal as it pointed at this big ball of stars just above the horizon.