- noun a cluster of densely packed stars, approximately spherical in shape, located within a spherical halo around the Milky Way galaxy
- Tight-packed type of star cluster – in contrast to the galactic clusters – which can contain 10,000 to over a million stars and which are found above and below the plane of the galaxy, but rarely near to it. Globular clusters are ancient objects at whose heart there may often lie a black hole (a thesis put forward because of X-rays observed coming from globular clusters). Their great age is shown by the spectra of globular cluster stars, which are poor in heavy elements, indicating that they formed when there were lower abundances of such elements than now. M3 in Canes Venatici is a well-known globular cluster. The stars in a globular cluster concentrate near its centre, where an observer would see a sky which was massively brighter than our own night sky.