Ground-based telescopes have allowed us to see that globular clusters are spherical, gravitationally bound clusters of up to a million stars, orbiting galaxies.
Study of the Milky Way's globulars has allowed us to pin-point the centre of the galaxy and measure its size and age.
This image of 47 Tucanae, a large globular cluster around 16,000 light years away, was taken by the 3.9-meter Anglo Australian Telescope.