Dynamical Behavior and Surface Features of Large Super-Fast Rotator Near-Earth Asteroid (436724) 2011 UW158

Abstract

The sub-kilometer Super-Fast Rotator and Potentially Hazardous Asteroid (436724) 2011 UW158 exhibits an extreme dynamical environment driven by its rotational period of 0.61072 h. Using a 3-D polyhedral shape model, we investigate the surface dynamic stability under both cohesionless and cohesion-modified conditions, while also addressing families of periodic orbits, station-keeping maneuvers, and energy states in this rapidly rotating, irregular-body regime. Our results show that, with the inclusion of cohesion, the effective slopes decrease to ~45°, permitting the retention of boulders with maximum sizes of ~50 m near the equatorial region. The dominance of the centrifugal term in the effective potential shifts the exterior equilibrium points inward, creating highly unstable geopotential regions where loose regolith is susceptible to ejection, preventing long-term surface retention outside the polar regions. To quantify this instability, we introduce the equivalent instability speed ($v_{\mathrm{ei}}$), extending conventional escape speed analyses to the SFR regime. These results are consistent with significant internal cohesion in 2011 UW158, which enables the body to maintain structural integrity under rotational stresses exceeding the classical spin barrier. Additionally, thermophysical modeling reveals that the super-fast rotation produces a nearly uniform surface temperature distribution. Finally, we apply a spherical harmonics method to compute families of periodic orbits around the asteroid to assess the fuel cost of station-keeping maneuvers at reduced computational cost. Overall, this study characterizes the dynamical environment of 2011 UW158, contributing to the understanding of Super-Fast Rotator asteroids recently identified in LSST survey images.