 These observations led to the explanation that it was part of a triple-star system consisting of two closely bound stars and one outer star.The black hole pulled the outer star away, which granted the star's momentum to the tight binary system and boosted both stars to escape velocity from the galaxy.As the stars traveled away, they went into normal stellar evolution, with one of them becoming a red giant and engulfing the other and forming one giant star — a blue straggler.