HIGH-RESOLUTION RESONANT STRUCTURE OF THE ASTEROID BELT

The synthetic orbital frequencies and eccentricities of main belt asteroids computed by Knezevic and Milani(1) and catalogued in the AstDys proper element database show evidence that the structure of the asteroid belt has been determined by a dense web of high-order resonances. By examining the orbital element distribution at high resolution, we show that the eccentricities of asteroids trapped in resonance tend to be higher than those of non-resonant asteroids. By analyzing how the observed increase in mean eccentricity depends on asteroid size, we also show that the effect decreases with increasing size and does not exist for asteroids with absolute magnitude less than 13.5. These observations can be accounted for by orbital evolution due to Yarkovsky forces and we argue that it is possible to use the observed increases in mean eccentricity to place limits on the strengths of those forces. The observations may also provide information on the ages of some families and on the variation of mean asteroid age with diameter.