Yarkovsky effect detection from ground-based astrometric data for near-Earth asteroid (469219) Kamo’oalewa

Abstract

Context. The Yarkovsky effect is a weak non-gravitational force but may significantly affect subkilometer-sized near-Earth asteroids. Yarkovsky-related drift may be detected, in principle, from astrometric or radar datasets of sufficient duration. To date, the asteroid Kamo'oalewa, the most stable of Earth's quasi-satellites, has an ∼ 18 year-long arc of ground-based optical astrometry. These data provide an opportunity to detect the Yarkovsky effect acting on the asteroid Kamo'oalewa. Aims. We determined the Yarkovsky-related drift of asteroid Kamo'oalewa from ∼ 18 years of ground-based optical astrometry. Furthermore, we investigated the influence of the Yarkovsky effect on the orbital evolution of asteroid Kamo'oalewa based on this estimated value, and evaluated the potential improvements in the detection of non-gravitational accelerations (Yarkovsky effect and solar radiation pressure) for the asteroid Kamo'oalewa that could be provided by the future Chinese small-body exploration mission, Tianwen-2. Methods. The Yarkovsky-related drift of asteroid Kamo'oalewa was detected from the orbital fitting of the astrometry measurements. We checked the Yarkovsky effect detection based on both the orbit fitting results and the physical mechanisms of the Yarkovsky effect. Results. We report for the first time the detection of the Yarkovsky effect acting on asteroid Kamo'oalewa based on ∼ 18 years of ground-based optical astrometry data. The estimated semi-major axis drift is (-6.155 ± 1.758) × 10 −3 au/Myr. In addition, our numerical simulation shows that the Yarkovsky effect has almost no influence on the short-term orbital evolution of the asteroid Kamo'oalewa, but does have a long-term influence, by delaying the entry of the object into the Earth co-orbital region and accelerating its exit from this region, with a more significant signature on the exit than on the entry. In the context of spacecraft tracking data, the Tianwen-2 mission will improve both non-gravitational accelerations (Yarkovsky effect and solar radiation pressure) and predictions of its future ephemeris.

Peculiar Orbital Characteristics of Earth Quasi-Satellite 469219 Kamo‘oalewa: Implications for the Yarkovsky Detection and Orbital Uncertainty Propagation

“…Figure 5 shows the respective probability density distributions of A 2 for the solutions S 7 and S 7 *, from which we can see that S 7 has a slightly lower estimate for the Yarkovsky drift than that of S 7 *, as well as a slightly larger uncertainty. Nevertheless, the result still indicates that A 2 is likely negative, suggesting that Kamo'oalewa is probably a retrograde rotator, which is consistent with that of Liu et al (2022). Note that the JPL Horizons online ephemeris system only presents a gravity-only solution (with a six-dimensional fit) for Kamo'oalewa (S J 6 ), which is listed in Table 2.…”

“…Since the orbit is limited to around 1 au, the uncertainty caused by other massive asteroids is negligible at the current accuracy. In addition, the oblateness perturbation of the Sun and Earth, as well as the solar radiation pressure, can also be safely ignored at the current level of observation accuracy (Liu et al 2022).…”

“…The effect for a 1 km sized object generally results in a subtle drift of ∼10 −3 au Myr −1 in the semimajor axis, with a related magnitude of acceleration close to the order of gravitational perturbation from the main belt (Nugent et al 2012). If accurate radar observations are available or optical observations cover a long arc, this effect can be detected from orbital fitting (Nugent et al 2012;Farnocchia et al 2013;Deo & Kushvah 2017;Greenberg et al 2017;Del Vigna et al 2018;Liu et al 2022). Greenberg et al (2020) presented the detection of the Yarkovsky effect for 247 near-Earth asteroids with optical and radar astrometry, and high-precision observations will reveal substantial detections (Chesley et al 2016;Desmars 2015;Dziadura et al 2022).…”

“…Recently, Liu et al (2022) presented the Yarkovsky detection for Kamo'oalewa using a modified open-source software. Here we aim to perform a comprehensive study of the Yarkovsky detection and understand orbital uncertainty propagation characteristics for Kamo'oalewa.…”

“…By implementing the latest debiasing technique ofEggl et al (2020) in the open-source OrbFit 5.0.7 package (http://adams. dm.unipi.it/orbfit/;Consortium et al 2011) and using the weighting scheme ofVereš et al (2017),Liu et al (2022)…”