Tag: nea

The von Zeipel-Lidov-Kozai (ZLK) mechanism drives secular oscillations of the eccentricity and inclination that can reshape the orbital architecture of small bodies throughout the Solar System. While the mechanism has been studied in detail for trans-Neptunian objects (TNOs), giant-planet satellites, and individual near-Earth objects, no systematic census of ZLK-resonant (ZLKR) asteroids inside Jupiter's orbit has been carried out. We aim to (i) identify all numbered asteroids with semimajor axes below the orbit of Jupiter that are currently trapped in the ZLK resonance for at least 100 kyr without leaving the resonance; (ii) test whether the universal coupling between the ZLK resonance and mean-motion resonances (MMRs) found for TNOs extends to the inner Solar System; and (iii) characterize the libration centers, libration periods, and dynamical peculiarities of the ZLKR population. We integrated the orbits of all 863,471 numbered asteroids with a < 4.9 au from the AstDyS catalog using the resonances Python package and the IAS15 adaptive-step integrator in a full N-body model that includes the Sun, the eight planets, and Pluto. The resonant angle of the ZLK resonance, σ ≡ ω, was analyzed in three integration phases (100 kyr automated, 500 kyr manual, and 100 kyr MMR identification for all candidates) and classified as regular, irregular, transient, slow-circulating, chaotic, or nonresonant. Two-body MMRs up to an order of 50 and three-body MMRs up to an order of 10 were then searched for with respect to every ZLKR candidate. We identified 201 asteroids (< 0.02% of the sample) that are currently in the ZLK resonance. Of these, 163 exhibit clean libration with a stable period and amplitude (i.e., regular), 38 formally librate but display evolving parameters (i.e., irregular), and an additional 26,309 objects fall into the broader 'possible' category. The ZLKR population is strongly concentrated in the near-Earth region (144 objects with perihelion q < 1.3 au) and among Mars-crossers (28 objects with 1.3 ≤ q < 1.66 au); the main belt is almost empty. In the contrast to the TNO region, where every known ZLKR object is simultaneously trapped in an MMR, only 11 of the 201 confirmed ZLKR asteroids are in a two-body or three-body MMR; meanwhile, the MMR-ZLK coupling is not only weak but appears decoupled inside Jupiter's orbit. About one-third of the confirmed ZLKR asteroids have inclinations below the classical quadrupole critical value of ∼39°, and several confirmed librators reach c₁ = (1 − e²) cos² i > 3/5. ZLKRs within 5 au behave differently from ZLK capture in the Kuiper belt: it is an overwhelmingly planet-crossing phenomenon that is decoupled from the MMR network and it extends below the classical critical inclination. The overall number of librators is significantly lower than in the TNO region. It appears that the interplay and overlapping between different resonances in the main belt suppresses long-lived ZLK libration.

Near-Earth asteroid 2024 YR₄ is a dynamically interesting object due to its predicted close approach to Earth in 2032 and its potential previous residence in mean-motion resonances (MMRs). We investigated the previous resonant status of 2024 YR₄ through numerical integrations backward for 100,000 years using a statistical approach with 1,000 virtual asteroids within the initial uncertainties and employing the ias15 (modified Everhart) integrator. The statistical analysis revealed a probability for 2024 YR₄ of 72% to have been trapped in the 3J-1 resonance in its previous dynamical history, including the nominal orbit. The resonance sticking phenomenon is evident; the asteroid experienced multiple temporary captures in various resonances. Beyond the dominant 3J-1 MMR, 16% of the simulated cases show capture in the 1M-2 resonance and 12% in the 2M+3J-5 resonance, but these secondary captures typically persist for only 2,000–10,000 years. These findings agree with existing models of near-Earth asteroid production, where chaotic diffusion arising from overlapping mean-motion and secular resonances transports objects from the main belt into near-Earth orbits.