blue horizontal branch star setâre-ye âbi-ye šâxe-ye ofoqi Fr.: étoile bleue de la branche horizontale A member of a population of blue stars appearing on the → horizontal branch in the → Hertzsprung-Russell diagram of the Galactic → halo populations and → globular clusters. Belonging to → spectral types B3 to A0, they have evolved past the → red giant stage and are burning helium in their core. → blue; → horizontal; → branch, → star. |