5 December 2008 16:55
- a large spherical group of stars bound together by gravity containing as few as ten thousand or as many as a million stars
- also known as globular star clusters, or sometimes just globs
- contrast with open clusters (aka, galactic clusters)
- all galaxies above a certain size are believed to be orbited by associated clusters
- the term was first used by William Herschel
- in general, clusters appear to contain stars of roughly the same age, and they appear to be some of the oldest stars known
- the Milky Way is estimated to have as many as 200 associated globular cluster, fewer than 160 have been discovered - the rest may not be visible from Earth
- a visualization of the Milky Way's globular clusters can be found here (scroll to the bottom)
- a few globular clusters are visible to the naked eye; Omega Centauri, for example, is a globular cluster masquerading as a star
