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Peer-reviewedCC BY 4.0The Astrophysical Journal Letters

JWST Characterization of Earth Quasi-satellite (469219) Kamo‘oalewa

  • Benjamin N. L. Sharkey1
  • Vishnu Reddy2
  • John W. Noonan3
  • Theodore Kareta4
  • James M. Bauer1
  • Bryan J. Holler5
  • Yaeji Kim1
  • Albert R. Conrad6
6 affiliations
  1. 1University of Maryland College Park
  2. 2University of Arizona
  3. 3Auburn University
  4. 4Villanova University
  5. 5Space Telescope Science Institute
  6. 6Large Binocular Telescope Observatory
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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 2026 February. The JWST reflectance spectrum is notably less red (more neutral) from 1.0 to 2.5 μ m than previous ground-based spectrophotometric observations. New observations made with the Large Binocular Telescope (LBT) in 2026 April, 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 μ m. We do not detect a 2.0 μ m silicate absorption. Models of Kamo‘oalewa’s faint thermal emission (beginning near 4.5 μ m) find a mean diameter of D = 18 ± 2 m and best-fit visible albedo p V = 0.5 9 − 0.17 + 0.25 , 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 provide 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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Cite

BibTeXRIS
BibTeX
@article{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},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = oct,
  doi = {10.3847/2041-8213/aea6b6},
  url = {https://iopscience.iop.org/article/10.3847/2041-8213/aea6b6},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
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  - 2026/10/14
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8213/aea6b6
UR  - https://iopscience.iop.org/article/10.3847/2041-8213/aea6b6
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 2026 February. The JWST reflectance spectrum is notably less red (more neutral) from 1.0 to 2.5 μ m than previous ground-based spectrophotometric observations. New observations made with the Large Binocular Telescope (LBT) in 2026 April, 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 μ m. We do not detect a 2.0 μ m silicate absorption. Models of Kamo‘oalewa’s faint thermal emission (beginning near 4.5 μ m) find a mean diameter of D = 18 ± 2 m and best-fit visible albedo p V = 0.5 9 − 0.17 + 0.25 , 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 provide independent confirmation of its rotation period of 27.9 minutes, with an axis ratio ∼1.4 ( D ∼ 15−21 m).
SN  - 2041-8205
SN  - 2041-8213
ER  -