What possible process can produce a blue straggler star?
Most of the brightest stars are older yellow stars, but a few young blue stars are also visible. This picture is a composite of three images taken by the Hubble Space Telescope.
A blue straggler star is a type of star found in old star clusters that appears younger and hotter than the other stars in the cluster, which have typically already evolved toward a cooler, reddish state.
While no single theory accounts for every instance, the primary proposed process is the coalescence of two lower-mass stars. In this scenario, the merger of two stars creates a single, more massive object. This combined mass alters the evolutionary state of the resulting star, effectively "restarting" its development and causing it to appear as a younger, more massive star located farther up the main sequence of the cluster's colour-magnitude diagram.12