Messier 11 is an open star cluster in the southern constellation of Scutum (The Shield). Messier 11 is also known as the Wild Duck Cluster, as the brightest of the 2,900 stars form a shape that somewhat resembles a flock of ducks in flight. Formed 220 million years ago, the cluster is 6,200 light-years from Earth and is the most distant open cluster visible to the naked eye. Charles Messier, the 18th century French astronomer, catalogued over 100 galaxies and clusters. Through the telescopes available at the time, comets, nebulae, globular clusters and galaxies appeared just as faint, diffuse blobs. This image was taken by the NASA/ESA Hubble Space Telescope.