Resonance Occupation in the Kuiper Belt: Case Examples of the 5:2 and 1:1 Resonances

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  • 22 January 2003
Abstract
We explore consequences of the previously unrecognized occupation of the exterior 5:2 and co-orbital 1:1 Neptunian mean-motion resonances (MMRs). Among all resonant Kuiper belt objects (KBOs), the three observed members of the 5:2 MMR discovered by our Deep Ecliptic Survey (DES) possess the largest semi-major axes (a = 55.4 AU), the highest eccentricities (e = 0.4), and substantial orbital inclinations (i = 10 deg). Their dynamically hot orbits, unlike hot orbits of previously known resonant KBOs, could not have originated from initially cold orbits that were modified purely by slow resonance sweeping by a migratory Neptune. Their existence most likely implies that Neptune migrated into a primordial Kuiper belt that was already pre-heated to large i,e > 0.2. By contrast, our first discovered Neptunian Trojan, 2001QR322, probably does not owe its existence to Neptune's migration at all. The trajectory of 2001QR322 is remarkably stable; the object can undergo tadpole-type libration about Neptune's leading Lagrange (L4) point for at least 1 Gyr. The long-term stability of our Trojan, and its insensitivity to large-scale changes in the orbital architecture of the solar system, lead us to regard the Neptunian 1:1 MMR as having shielded 2001QR322 from dynamical excitation processes that afflicted the remainder of the Kuiper belt.

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