and relationship to the parent body. Computer simulations of the collision are more consistent with Eunomia being a re-accumulation of most of the fragments of a completely shattered parent body, yet Eunomia's quite high density would indicate that it is not a rubble pile after all. Whatever the case in this respect, it appears that any metallic core region, if present, has not been exposed. An older explanation of the compositional differences, that Eunomia is a mantle fragment of a far larger parent body (with a bit of crust on one end, and a bit of core on the other), appears to be ruled out by studies of the mass distribution of the entire Eunomia family. These indicate that the largest fragment (that is, Eunomia) has about 70% of the mass of the parent body, which is consistent with Eunomia being a central remnant, with the crust and part of the mantle stripped off. These indications are also in accord with recent mass determinations which indicate that Eunomia's density is typical of mostly intact stony asteroids, and not the anomalously low "rubble pile" density of ~ that had been reported earlier. Studies 15 Eunomia was in study of asteroids using the Hubble FGS. Asteroids studied include (63) Ausonia, (15) Eunomia, (43) Ariadne, (44) Nysa, and (624) Hektor. Orbit The orbit of 15 Eunomia places it in a 7:16 mean-motion resonance with the planet Mars. Eunomia is used by the Minor Planet Center to calculate perturbations. The computed Lyapunov time for this asteroid is 25,000 years, indicating that it occupies a chaotic orbit that will change randomly over time because of gravitational perturbations of the planets. Eunomia has been observed occulting stars three times. It has a mean opposition magnitude of +8.5, about equal to the mean brightness of Titan, and can reach +7.9 at a near perihelion opposition. Asteroid passed about from Eunomia on March 4, 2002. See also Former classification of planets References External links shape model deduced from lightcurve, including composition variations across the surface (displays Elong from Sun and V mag for 2011) Eunomia asteroids Eunomia Eunomia S-type asteroids (Tholen) S-type asteroids (SMASS) 18510729