A survey with the Anglo-Australian Telescope (AAT) has revealed dozens of miniature galaxies the nearby Fornax galaxy cluster. These are a class of galaxies known as "ultra compact dwarfs" (UCDs). These objects were completely unknown until a few years ago, and now astronomers believe that they are very common. Perhaps they are leftover primordial building blocks that merged together to form larger galaxies. They are incredibly small, only about 120 light-years across, but they can contain tens of millions of stars.