A highly resonant Neptunian region: A systematic search for two-body and three-body mean-motion resonances

In this study, a large-scale numerical investigation of resonant objects in the Neptune region is presented, focusing on both two-body and three-body mean-motion resonances (MMRs). Two separate simulations were conducted to identify resonant populations and quantify their prevalence. In Simulation 1, two-body MMRs with Uranus and Neptune up to the resonant order q ≤ 10 , as well as three-body MMRs involving both planets up to the order q ≤ 6 , were examined. Using automated resonance classification techniques, it was found that 42.1% of objects are resonant, increasing to 58.2% when including controversial cases. This is significantly higher than the resonant fraction observed in the main asteroid belt . The results confirm that two-body MMRs with Neptune dominate, with a smaller but significant fraction of three-body resonances and two-body resonances with Uranus. In Simulation 2, the analysis was extended to higher-order ( q ≤ 20 ) and high-integer-coefficient ( m i ≤ 50 ) two-body resonances with Neptune, testing whether previously classified non-resonant objects might belong to higher-order MMRs. This second simulation revealed an additional 108 resonances and 104 new confirmed resonant objects, bringing the total fraction of resonant asteroids in the region to 49.3% confirmed cases and 65.1% with controversial cases included. Many new two-body MMRs with Neptune are found. Notably, some objects were found to be trapped in multiple resonances simultaneously. These results demonstrate that MMRs play an important role in shaping the trans-Neptunian region, with an overall resonance fraction more than three times higher than in the main asteroid belt . All objects in this region may be in fact resonant. • The TNO region has a highly resonant structure, with up to 65.1% of resonant asteroids. • More than 100 new high-order and high-integer mean-motion resonances have been identified. • New two-body MMRs have been found: 6N-5, 3N-10, 7N-11, 9N-16, 5N-13, 7N-23, and 25N-43 and others. • New three-body MMRs include 4U-5N-5, 3U-3N-5, 3U-2N-6, 5U-5N-6, etc. • Some asteroids are simultaneously trapped in two different resonances, e.g., 602715 and 535230.