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15 Eunomia

An asteroid of the main Asteroid Belt discovered in 1851, just two months after asteroid Irene, and like Irene named for one of the three sisters from Greek mythology known as the Horae or 'Hours'. The third sister, Dike, also gave her name to an asteroid discovered some seventeen years later.

Eunomia is relatively regular in shape, but not entirely spherical, and has a form defined by several edges and faces. Its longest axis is about 330km, making it the largest of the stony asteroids, a common type within the Asteroid Belt.

Rocky Eunomia represents the core of larger body of the ancient Solar System, a body that evidently suffered several major impacts before a final cataclysmic collision broke it into many fragments. Eunomia itself represents more than two thirds of the mass left over from this collision, with the remainder spread out through the Asteroid Belt to form the Eunomia family, also called the Eunomian asteroids.

There are about 4,700 of these Eunomian asteroids in total, all belonging to the stony S-type classification. The others are much less massive than Eunomia itself, with the largest examples being Tyche and Alma, with diameters of about 65km and 25km respectively. Several other asteroids (such as Lumen or Io) also share the orbital characteristics of the Eunomia family, and are sometimes listed as members. These 'interlopers', however, do not appear to have formed part of the original object that broke apart to leave Eunomia and thousands of other fragmentary remnants swirling through the Asteroid Belt.


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