THE RESONANT STRUCTURE OF THE KUIPER BELT AND THE DYNAMICS OF THE FIRST 5 TRANS-NEPTUNIAN OBJECTS

By means of simple analytic models and numerical integrations, we expl ore the resonant structure of the Kuiper belt. We find that the inner order-one mean motion resonances with Neptune are very stable and give phase-protection from close encounters with Neptune. The 2/3 resonanc e is very complex and stable only at small amplitude of libration. The overlapping secular resonances at 36 and 41 AU give rise to large inc reases in the eccentricity, and therefore to orbits that are very unst able. Furthermore, we integrate numerically the motion of the first fi ve Kuiper belt objects, the orbits of which have been recently tempora rily determined, and we analyze their orbital evolution with respect t o resonances. The three objects 1993SB, 1993SC, and 1993RO are in the 2/3 resonance, and, of these, the first two have a very regular evolut ion. Conversely, 1993RO is chaotic, and is expelled from the 2/3 reson ance, encountering Neptune after 320 Myr. The object 1992QB1 is very r egular and outside all resonances. Finally, 1993FW is chaotic, due to the 4/7 resonance and to a secondary secular resonance. The eccentrici ty, however, is limited below 0.2, so that the body does not encounter Neptune. We stress that, since the orbital elements of these five obj ects are very uncertain, our results should be considered only as indi cations of possible dynamical evolutions in the Kuiper belt. (C) 1995 Academic Press,Inc.