Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa

León

et al. 2023

A&A

Context. The near-Earth orbital space is shared by natural objects and space debris that can be temporarily captured in geocentric orbits. Short-term natural satellites are often called mini-moons. Reflectance spectroscopy can determine the true nature of transient satellites because the spectral signatures of spacecraft materials and near-Earth asteroids (NEAs) are different. The recently discovered object 2022 NX1 follows an Earth-like orbit that turns it into a recurrent but ephemeral Earth companion. It has been suggested that 2022 NX1 could have an artificial origin or be lunar ejecta. Aims. Here, we use reflectance spectroscopy and N-body simulations to determine the nature and actual origin of 2022 NX1. Methods. We carried out an observational study of 2022 NX1, using the OSIRIS camera spectrograph at the 10.4 m Gran Telescopio Canarias, to derive its spectral class. N-body simulations were also performed to investigate how it reached NEA space. Results. The reflectance spectrum of 2022 NX1 is neither compatible with an artificial origin nor lunar ejecta; it is also different from the V type of the only other mini-moon with available spectroscopy, 2020 CD3. The visible spectrum of 2022 NX1 is consistent with that of a K-type asteroid, although it could also be classified as an Xk type. Considering typical values of the similar albedo of both K-type and Xk-type asteroids and its absolute magnitude, 2022 NX1 may have a size range of 5 to 15 m. We confirm that 2022 NX1 inhabits the rim of Earth’s co-orbital space, the 1:1 mean-motion resonance, and experiences recurrent co-orbital engagements of the horseshoe-type and mini-moon events. Conclusions. The discovery of 2022 NX1 confirms that mini-moons can be larger than a few meters and also that they belong to a heterogeneous population in terms of surface composition.

Section: Discussionsupporting

confidence: 66%

Mini-moons from horseshoes: A physical characterization of 2022 NX₁ with OSIRIS at the 10.4 m Gran Telescopio Canarias

León

et al. 2023

A&A

“…The diameter of 36 m was estimated from the absolute magnitude (see Table 1) following the relationship: D = 1329 km ×10 −H/5 × 1 √ p v (Pravec & Harris 2007). A density of 2.120 g/cm 3 was assumed (Del Vigna et al 2018), with reference to S-type asteroids (Fohring et al 2018;Sharkey et al 2021). The obliquity was assumed as 0 or 180 deg to ensure that the expected maximum absolute Yarkovskyrelated value of semi-major axis drift for HO3 was obtained.…”

Section: The External Assessment Of the Yarkovsky Detectionmentioning

confidence: 99%

“…The simulated range measurements were performed at monthly intervals from 2025 December 01 to 2026 July 01. Asteroid HO3 is also favourably placed for observations once a year around April when it becomes sufficiently bright (with visual magnitude V < 23.0 mag) to be observed by large telescopes on Earth (Sharkey et al 2021). Therefore, we also simulated one-night ground-based optical astrometry by a large telescope in mid-April each year from 2022 to 2026.…”

Section: The Chinese Small Body Exploration Missionmentioning

confidence: 99%

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

Liu

Yan

et al. 2022

A&A

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.

“…The latest research showed that the semimajor axis drift of Kamo'oalewa produced by the Yarkovsky effect could cause a faster removal from the Earth co-orbital zone (Fenucci and Novaković 2021). Sharkey et al (2021) proposed a possibility for Kamo'oalewa's origin: it originates in the Earth-Moon system, perhaps as impact ejecta from the lunar surface or as a fragment of a parent near-Earth objects tidal or rotational break-up during a close encounter with the Earth-Moon system. Its reflectance spectrum and the low value of the relative velocity with respect to Earth lends support to the lunar ejecta hypothesis.…”

mentioning

confidence: 99%

Stability Analysis of Earth Co-orbital Objects

Dong

2022

In this paper, we investigate the stability of Earth co-orbital objects (ECOs) based on the torus structure. The Hamiltonian value is an index to evaluate co-orbital stability. According to topological characters of tadpole (TP), horseshoe (HS), quasi-satellite (QS), and critical compound surfaces in the torus space, the co-orbital area is divided into several regions in detail. We select 221 potential ECOs as representative samples. Numerical integration in the Sun–Earth system illustrates that most of objects above the collision line are short- or long-term stable ECOs in the QS–HS and QS–TP motions, and most of objects in the unstable region are unstable ones, which is in agreement with our semi-analytical conclusions. The stability of an ECO with a larger Hamiltonian value could be stronger. An efficient method to determine the long-term co-orbital stability of a potential ECO is proposed without long-term numerical integration. Numerical integration in the multiplanet model demonstrates that our stability analysis is still applicable for the real solar system. As an application of our stability analysis, two well-determined QS–HS ECOs above the collision line are identified and analyzed for the first time. For instance, the QS–HS state of 2019 VL5 can be sustained for more than 3000 yr, and its current HS state will be sustained for at least 800 yr.