The spectral slope of Kamoʻoalewa is even redder than the slope of these objects. Sw-types exhibit the same characteristics as S-types but have redder slopes in the infrared 23. 2 shows the spectrum of Kamoʻoalewa with that of Sw-type asteroid (63) Ausonia 21, 22. The spectral slope of Kamoʻoalewa is redder (higher reflectance at increasing wavelength) than typical S-type asteroid spectra as defined by the Bus-Demeo taxonomy. We used curve matching to constrain the surface composition and identify possible analog materials for Kamoʻoalewa. The error bars for the zJHK colors represent the errors in the color ratio measurements (independent measurements were made of z/H, J/H, J/K). The error bars shown for the spectrum are the photometric uncertainties at the spectral resolution as shown. Spectra were normalized to unity at 0.7 µm.
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The gray shaded region indicates wavelengths with time-variable telluric features that can introduce artifacts in the data. The steeply red-sloped spectrum we observe is consistent with a highly space-weathered silicate surface, similar to that of lunar samples. Our data shows a spectrum differing strongly from reddened silicate-rich asteroid spectra, exemplified by the Sw-type (63) Ausonia 21, 22.
#The week magazine 2016 mods#
Black circles indicate the spectrum collected using the MODS instrument in 2017 (0.4–0.95 µm), and black triangles indicate the infrared spectrum collected using the LUCI instrument in 2019 (0.95–1.25 µm). Previous study of plausible shape and rotation models for Kamoʻoalewa found that Kamoʻoalewa’s surface may retain grains smaller than ~1 mm-1 cm in size 20.Ĭomparison of VNIR reflectance spectrum of Kamoʻoalewa with that of a virtual mixture of the meteorites Gibeon and Vaca Muerta and the reflectance spectrum of lunar highlands sample #14163 (grain size 20–45 µm) returned from the Apollo 14 mission 59. These observations provided an initial assessment of the quasi-satellite’s taxonomic class as being consistent with S- and L-type silicate asteroids 13 and rotation period, which was determined to be 21.0 mag rotate fast enough to imply internal cohesion 19, illustrated by curves indicating the maximum spin speed of an object at a given size given a range of assumed object bulk densities ( \(\)) and tensile strength coefficients ( \(\kappa\)). The Multi-Object Double Spectrograph (MODS) instrument was used in imaging and long-slit spectroscopic modes 12 to carry out our observations.
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We used the LBT to obtain broadband color photometry and visible spectra on UT 14 April 2017.
#The week magazine 2016 windows#
These regular observing windows allow for continued study, unlike temporarily captured minimoons such as 2020 CD 3 that require dedicated observing campaigns during a single apparition shortly after their discovery 10, 11. Uniquely, Kamoʻoalewa is favorably placed for observations once a year around April when it becomes bright enough (with visual magnitude V < 23.0mag) to be characterized by large telescopes on Earth. Physical characterization of the quasi-satellite population has been lacking due to challenging observing geometry and short residence time in near-Earth space. Study of this class of objects began with the initial discovery of (164207) 2004 GU 9 7, 8, 9. 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. As a quasi-satellite, the orbit of Kamoʻoalewa 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, 4, 5. Near-Earth object (NEO) (469219) Kamoʻoalewa (provisional designation 2016 HO 3) is the most stable of the five known quasi-satellites of the Earth, with a dynamical lifetime of a few hundred years 1.