A BRIDGE BETWEEN SECONDARY AND SECULAR RESONANCES INSIDE THE HECUBA GAP

The location of the secondary and secular resonances inside the three- dimensional 2:1 mean motion resonance with Jupiter is investigated bot h analytically and numerically. A bridge between the low-eccentric sec ondary-resonance belt and the high-eccentric secular-resonance complex is found and its mechanism analyzed. This bridge is the crucial link in the path taken by the orbit displayed by Wisdom (1987-see Fig. 19) to show the importance of the third dimension in this problem. This br idge being identified and located, we can recognize that ''under it'' lies a region of phase space which seems to be protected from close en counters with planets. (C) 1995 Academic Press,Inc.