JWST Characterization of Earth Quasi-Satellite (469219) Kamo`oalewa
Abstract
Near-Earth asteroid (469219) Kamo`oalewa is a uniquely stable quasi-satellite of the Earth and a target of the Tianwen-2 spacecraft mission. Here we report observations taken with JWST's NIRSpec instrument in integral field unit (IFU) mode in February 2026. The JWST reflectance spectrum is notably less red (more neutral) from 1.0−2.5 μm than previous ground-based spectrophotometric observations. New observations made with LBT in April 2026, observed and processed similarly to the 2021 observations, find zJ colors in agreement with JWST. Kamo`oalewa's infrared colors appear more similar to typical silicate-rich asteroids and unlike the reddened, space-weathered lunar-like silicates suggested by previous observations. In agreement with the ground-based spectrum, we detect a faint silicate absorption feature at 0.93± 0.01 μm. We do not detect a 2.0 μm silicate absorption. Models of Kamo`oalewa's faint thermal emission (beginning near 4.5 μm) find a mean diameter of D=18±2m and best-fit visible albedo pV = 0.59+0.25−0.17, with models as low as pV = 0.36 providing adequate model fits. This combination of color, albedo, and absorption bands is similar to oldhamite-bearing enstatite-rich compositions. Kamo`oalewa's brightness variations over the course of the JWST program provides independent confirmation of its rotation period of 27.9 minutes, with an axis ratio ∼1.4 (D∼15−21 m).
Versions
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BibTeX
@misc{sharkey2026jwst,
title = {{JWST Characterization of Earth Quasi-Satellite (469219) Kamo`oalewa}},
author = {Benjamin N. L Sharkey and Vishnu Reddy and John W. Noonan and Theodore Kareta and James M. Bauer and Bryan J. Holler and Yaeji Kim and Albert R Conrad},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.24017},
eprint = {2606.24017},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.24017},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - JWST Characterization of Earth Quasi-Satellite (469219) Kamo`oalewa
AU - Benjamin N. L Sharkey
AU - Vishnu Reddy
AU - John W. Noonan
AU - Theodore Kareta
AU - James M. Bauer
AU - Bryan J. Holler
AU - Yaeji Kim
AU - Albert R Conrad
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2606.24017
UR - https://arxiv.org/abs/2606.24017
AB - Near-Earth asteroid (469219) Kamo`oalewa is a uniquely stable quasi-satellite of the Earth and a target of the Tianwen-2 spacecraft mission. Here we report observations taken with JWST's NIRSpec instrument in integral field unit (IFU) mode in February 2026. The JWST reflectance spectrum is notably less red (more neutral) from 1.0−2.5 μm than previous ground-based spectrophotometric observations. New observations made with LBT in April 2026, observed and processed similarly to the 2021 observations, find zJ colors in agreement with JWST. Kamo`oalewa's infrared colors appear more similar to typical silicate-rich asteroids and unlike the reddened, space-weathered lunar-like silicates suggested by previous observations. In agreement with the ground-based spectrum, we detect a faint silicate absorption feature at 0.93± 0.01 μm. We do not detect a 2.0 μm silicate absorption. Models of Kamo`oalewa's faint thermal emission (beginning near 4.5 μm) find a mean diameter of D=18±2m and best-fit visible albedo p_V = 0.59^+0.25_−0.17, with models as low as p_V = 0.36 providing adequate model fits. This combination of color, albedo, and absorption bands is similar to oldhamite-bearing enstatite-rich compositions. Kamo`oalewa's brightness variations over the course of the JWST program provides independent confirmation of its rotation period of 27.9 minutes, with an axis ratio ∼1.4 (D∼15−21 m).
ER -