Please note that the content of this book primarily consists of articles
available from Wikipedia or other free sources online. Blue stragglers
(BSS) are main sequence stars in open or globular clusters that are more
luminous and bluer than stars at the main sequence turn-off point for
the cluster. Blue stragglers were first discovered by Allan Sandage in
1953 while performing photometry of the stars in the globular cluster
M3. Standard theories of stellar evolution hold that the position of a
star on the Hertzsprung-Russell diagram should be determined almost
entirely by the initial mass of the star and its age. In a cluster,
stars all formed at approximately the same time, and thus in an H-R
diagram for a cluster, all stars should lie along a clearly defined
curve set by the age of the cluster, with the positions of individual
stars on that curve determined solely by their initial mass.
