A group of asteroids whose members have very similar orbital characteristics (semimajor axis, eccentricity, and inclination), and are believed to share a common origin. Examples are the Eos family, the Koronis family, the Themis family, the Maria family, and members of the Flora group. Hirayama families are thought to result from the break-up of larger asteroids several hundred kilometres in size following catastrophic collisions. They are named after the Japanese astronomer Kiyotsugu Hirayama (1874–1943), who demonstrated their existence in 1918.
Subjects: Astronomy and Astrophysics.