A Hirayama family of asteroids in the outer part of the main asteroid belt at a mean distance of 3.13 AU from the Sun. It is one of the most populous and best-defined families, consisting of a core of large objects surrounded by a cloud of predominantly smaller ones. The core includes (24) Themis, (62) Erato, (90) Antiope, (468) Lina, (526) Jena, and (846) Lipperta. Most family members have low albedos and are of the carbonaceous C class. Themis itself is a C-class asteroid, diameter 198 km, discovered in 1853 by the Italian astronomer Annibale de Gasparis (1819–92). It is the first asteroid discovered to have water ice on its surface. The orbit of Themis has a semimajor axis of 3.129 AU, period 5.54 years, perihelion 2.72 AU, aphelion 3.54 AU, and inclination 0°.8.
Subjects: Astronomy and Astrophysics.