<P> The ultimate fate of a globular cluster must be either to accrete stars at its core, causing its steady contraction, or gradual shedding of stars from its outer layers . </P> <P> The distinction between cluster types is not always clear - cut, and objects have been found that blur the lines between the categories . For example, BH 176 in the southern part of the Milky Way has properties of both an open and a globular cluster . </P> <P> In 2005, astronomers discovered a completely new type of star cluster in the Andromeda Galaxy, which is, in several ways, very similar to globular clusters . The new - found clusters contain hundreds of thousands of stars, a similar number to that found in globular clusters . The clusters share other characteristics with globular clusters such as stellar populations and metallicity . What distinguishes them from the globular clusters is that they are much larger--several hundred light - years across--and hundreds of times less dense . The distances between the stars are, therefore, much greater within the newly discovered extended clusters . Parametrically, these clusters lie somewhere between a globular cluster and a dwarf spheroidal galaxy . </P> <P> How these clusters are formed is not yet known, but their formation might well be related to that of globular clusters . Why M31 has such clusters, while the Milky Way does not, is not yet known . It is also unknown if any other galaxy contains these types of clusters, but it would be very unlikely that M31 is the sole galaxy with extended clusters . </P>

The characteristic of a globular cluster of stars is