Eunomia

Eunomia is the largest S-type asteroid in the solar system with a diameter of 270 km, orbiting at 2.64 AU in the middle of the asteroid belt. It is the parent body of the Eunomia asteroid family, one of the most prominent families in the intermediate belt. Eunomia's surface is composed of silicates, nickel-iron, calcium-rich pyroxenes, and olivine — indicating it is a partially differentiated body that experienced internal heating early in its history. The current asteroid is thought to be the central remnant of a larger parent body that was shattered by a catastrophic collision, with the Eunomia family members being the scattered fragments. Eunomia has an elongated shape and shows significant brightness variations as it rotates.

At opposition, Eunomia reaches about magnitude 7.9, requiring binoculars or a small telescope. Its brightness ranges from magnitude 8 to 10 depending on its position in orbit. Eunomia's elongated shape causes noticeable brightness variations during its 6-hour rotation — advanced observers can detect these with careful photometric measurements. Best viewed from September through November around opposition, which occurs roughly every 16 months. Its middle-belt position gives it a moderate apparent speed against the star field. Use an ephemeris to track its position and identify it through nightly motion.

Eunomia was discovered on July 29, 1851 by Italian astronomer Annibale de Gasparis at the Capodimonte Observatory in Naples — the same astronomer who had discovered Hygiea two years earlier. It was the fifteenth asteroid discovered and was named after Eunomia, one of the Horae (Hours) in Greek mythology, a goddess representing order and lawful conduct. De Gasparis was a remarkably successful asteroid hunter, discovering nine asteroids between 1849 and 1865. No spacecraft has visited Eunomia.