called ΓÇ£blue stragglersΓÇ¥ because they are bright in ultraviolet. Most stars this old have less mass and a cooler outer surface and so are relatively faint in ultraviolet. The stars shown here are thought to be the exposed cores of older stars whose outer envelopes have been ripped away by close encounters or collisions with other stars. Since the blue stragglers are concentrated in the clusterΓÇÖs center, one can infer that they are massive and may even be binaries.
