Coathanger star cluster, optical image. This cluster, also known as Brocchi's Cluster and Collinder 399, is named for its distinctive shape. The coathanger is formed of the horizontal line of stars across centre and the hook of four stars below it. Once thought to be a true star cluster, in which the stars all formed from the same cloud of gas, modern measurements have shown the stars to be at different distances, implying that it is just a chance alignment of stars rather than a true cluster. Such a grouping of unrelated stars into a pattern is known as an asterism. The cluster is found in the constellation Vulpecula.