How do astronomers explain the existence of blue stragglers?

A blue straggler is a large star with more than twice the expected mass for stars in the cluster; these stars are found in open or globular clusters and do not fit the pattern of the other stars in the cluster.

The most common explanation for blue stragglers is that they result from collisions between two stars or from a star colliding with another equally massive object. One possible scenario is a close binary star system in which the stars collide; additionally, blue stragglers are more likely to occur in densely populated areas where stars are close to one another and can collide easily.

Blue stragglers are thought to form through processes such as stellar collisions, mass transfer in binary star systems, or mergers of binary stars. These interactions can rejuvenate or prolong the lifetimes of stars, making them appear younger and bluer than other stars in the cluster. Astronomers explain the existence of blue stragglers as the result of stellar interactions within dense stellar environments, such as globular clusters.