2026/08/01 by Xiaoyu Sun, Zhijun Song, Hanjie Tan +8
Physics and Astronomy · #astro-ph.EP
Submitted to ApJL
arxiv created 2026/08/01 · arxiv updated 2026/08/04
(469219) Kamo`oalewa is the most stable Earth quasi-satellite and the target of China's Tianwen-2 asteroid sample return mission. Due to its small size, fast rotation, and the limited observing geometry accessible from the ground, many physical properties of Kamo`oalewa remain poorly constrained, including the rotational status and shape. We obtained three epochs of high-cadence, high signal-to-noise photometric lightcurves of Kamo`oalewa with the Gemini North Telescope from 2026 April to May, supplemented by one lightcurve from the Lowell Discovery Telescope in 2026 May. Our analysis suggests that Kamo`oalewa is in a non-principal-axis rotation with an elongated shape. Four possible solutions exist, including a long-axis mode (LAM) solution and a short-axis mode (SAM) solution, as well as their corresponding mirrored angular momentum directions. The most preferable solution has a LAM model with a precession period Pϕ=27.65± min, and a rotational period Pψ=50.49±0.08min, and the angular momentum points to ecliptic coordinates (λ, β) = (226o ± 20o, -39o ± 15o), although we cannot rule out other solutions or other close-by periods due to aliasing. We also derived a convex shape inversion for LAM with consistent rotational parameters but could not find a satisfactory inversion for SAM. The non-principal-axis rotation provides additional constraints on the dynamic history or the internal structure of Kamo`oalewa.