Named in honor of Yusuke Hagihara {1897–1979}, professor of astronomy at the University of Tokyo from 1935 to 1957, Director of the Tokyo Observatory from 1946 to 1957, and long an inspiring leader and teacher, principally in celestial mechanics and also in several other branches of astronomy and astrophysics. Best known for his theory of libratory motions and general discussion of stability problems in celestial mechanics, he has also made important contributions to the study of the velocity distribution of free electrons in planetary nebulae. In recent years he has produced a monumental five-volume treatise on celestial mechanics. He served as a vice-president of the IAU during 1961–1967 and as president of Commission 7 during 1964–1967. (M 4419) _ _.