Globular clusters are compact groups of stars found in the haloes of g
alaxies. For the clusters in the Milky Way, a combination of the best
available observational data and models of stellar evolution indicates
that they are among the oldest objects in our Galaxy, with an age of
approximately 13 billion years. this age roughly coincides with recent
estimates of the age of a low-density, freely expanding Universe. The
ages of the globular clusters may therefore provide a critical test o
f cosmological models, although this must await more accurate distance
(and hence age) determinations. Improved age estimates should also he
lp determine whether the halo of our Galaxy formed from accreted dwarf
galaxies or through the collapse of a spherical protogalactic cloud.