A dynamical solution of the triple asteroid system (45) Eugenia

We present the first dynamical solution of the triple asteroid system (45) Eugenia and its two moons Petit-Prince (diameter similar to 7 km) and S/2004 (45) 1 (diameter similar to 5 km). The two moons orbit at 1165 and 610 km from the primary, describing an almost-circular orbit (e similar to 6 x 10(-3) and e similar to 7 x 10(-2) respectively). The system is quite different from the other known triple systems in the main belt since the inclinations of the moon orbits are sizeable (9 degrees and 18 degrees with respect to the equator of the primary respectively). No resonances, neither secular nor due to Lidov-Kozai mechanism, were detected in our dynamical solution, suggesting that these inclinations are not due to excitation modes between the primary and the moons. A 10-year evolution study shows that the orbits are slightly affected by perturbations from the Sun, and to a lesser extent by mutual interactions between the moons. The estimated J(2) of the primary is three times lower than the theoretical one, calculated assuming the shape of the primary and an homogeneous interior, possibly suggesting the importance of other gravitational harmonics. (C) 2010 Elsevier Inc. All rights reserved.