Abstract
Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe. Here we use the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT) to conduct a comprehensive physical characterization of quasi-satellite (469219) Kamoʻoalewa and assess its affinity with other groups of near-Earth objects. We find that (469219) Kamoʻoalewa rotates with a period of 28.3 (+1.8/−1.3) minutes and displays a reddened reflectance spectrum from 0.4–2.2 microns. This spectrum is indicative of a silicate-based composition, but with reddening beyond what is typically seen amongst asteroids in the inner solar system. We compare the spectrum to those of several material analogs and conclude that the best match is with lunar-like silicates. This interpretation implies extensive space weathering and raises the prospect that Kamo’oalewa could comprise lunar material.
Highlights
Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe
The Multi-Object Double Spectrograph (MODS) instrument was used in imaging and longslit spectroscopic modes[12] to carry out our observations
Follow-up broadband photometry was collected on UT 18 April 2017 at Lowell Discovery Telescope (LDT) in the VR filter using the Large Monolithic Imager[15]
Summary
Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe. As a quasi-satellite, the orbit of Kamooalewa is very Earth-like, with semi-major axis within 0.001 au of Earth’s, a low eccentricity of just ~0.1, and a modest inclination of about 8 degrees to the ecliptic[2] and it is a frequently proposed target for spacecraft study[3–5]. As it orbits the Sun with a ~1 year orbital period, it takes a quasi-satellite path relative to Earth, that is, it makes retrograde loops around Earth with a ~1 year period but well beyond Earth’s Hill sphere[6]. These regular observing windows allow for continued study, unlike temporarily captured minimoons such as 2020 CD3 that require dedicated observing campaigns during a single apparition shortly after their discovery[10,11]
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