Globular clusters are clusters of stars, arranged into a sphere. They contain tens of thousands of stars, packed very closely together, so that when viewed from the Earth, their core’s appear as a single glowing mass. Globular clusters are arranged in a vast spherical halo around their parent galaxy. Our own Milky Way galaxy has a little over 150 globular clusters, but larger galaxies can have many more than that. They tend to be very old – at least as old as their parent galaxy – which know because their stars are all old and red, with no hot young stars visible. The largest globular visible from Earth is Omega Centauri (ω centauri), and appears to the naked eye as a fuzzy star in the constellation Centaurus. It contains millions of stars, and is visibly flattened, leading some astronomers to suggest that it may actually be the core of a dwarf galaxy that was cannibalised by the Milky Way.