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 HertzsprungâRussell 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 HâR 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. With masses two to three times that of the rest of the main-sequence cluster stars, blue stragglers seem to be exceptions to this rule. The resolution of this problem is likely related to interactions between two or more stars in the dense confines of the clusters in which blue stragglers are found.
You may or may not have heard about blue stragglers; they are blue stars that are hotter and bluer than other stars with the same luminosity. Until now, it seemed that these stars defied most if not all of the standard stellar theories, but scientists now believe they have finally solved this stellar mistery. The [...]