Core of globular cluster 47 Tucanae, Hubble Space Telescope image. The density of stars at the core of a globular cluster can be 10,000 times greater than that in our region of the galaxy. There would be 10,000 stars in the night sky closer to us than our nearest star. This image was part of a survey used to track the motions of stars in globular clusters. It was found that heavier stars sink towards the centre, and lighter stars move outwards. This globular cluster is 15,000 light years from Earth, in the constellation Tucana. This image was obtained with Hubble's Advanced Camera for Surveys instrument. The results were published in October 2006.