A Hirayama family of asteroids in the outer region of the main asteroid belt at a mean distance of 3.02 AU from the Sun. Most Eos family members have surface properties roughly intermediate between S and C types, leaning towards the S type especially in albedo. The family is named after (221) Eos, an S-class asteroid, diameter 104 km, discovered in 1882 by the Austrian astronomer Johann Palisa (1848–1925). Its orbit has a semimajor axis of 3.014 AU, period 5.23 years, perihelion 2.70 AU, aphelion 3.33 AU, and inclination 10°.9.
Subjects: Astronomy and Astrophysics.