What are blue stragglers and how are they detected?
Blue stragglers are stars in open clusters or globular clusters which don't fit the pattern of the other stars.
Stars in open clusters and globular clusters all formed around the same time. They are main sequence stars and their brightness and color should be determined by the Stars' initial mass.
Blue stragglers are stars which don't fit the pattern because they are too luminous and too blue colored to fit the pattern. This makes them stand out from other stars.
It is thought that they were created by the collision of stars.