A blue main-sequence star, usually found in a globular or open cluster that appears to be slower in its evolution than other stars of similar mass and luminosity in the same cluster. On the Hertzsprung–Russell diagram, blue stragglers are found on the main sequence above the turnoff point of the cluster. They are thought to form either through mass transfer in a binary system or through merger of two stars. The latter process occurs either through direct collision of two single stars or through the merger of the two stars in a binary.
Subjects: Astronomy and Astrophysics.