The asteroid was discovered by Pan-STARRS at Haleakala Observatory on 27 April 2016. Numerous proposed missions have since targeted the object, including a NASA solar-sail mission,[7] a University of Colorado flyby and impact experiment,[8] and was selected as a target for the Chinese ZhengHe[9] which has turned into the Tianwen-2 mission.[10] The chondriticsimulants QLS-1, 2, and 3 have been developed by the Qian Xuesen Laboratory of Space Technology to better prepare for these missions.[11] In an ambitious proposal, 469219 Kamo’oalewa is even considered for use as a space station for Earth-to-Mars travel.[12]
The name Kamoʻoalewa is derived from the Hawaiian words ka 'the', moʻo 'fragment', referring to it being a piece broken off a larger object, a 'of', and lewa 'to oscillate', referring to its motion in the sky as viewed from Earth.[22][23] The official naming citation was published by the Minor Planet Center on 6 April 2019 (M.P.C. 112435).[24]
Orbit and classification
Kamoʻoalewa orbits the Sun at a distance of 0.90–1.10 AU. Although the period as of 2022 is about 366 days, its longer-term average period is closer to 365 days. 469219 Kamoʻoalewa is a quasi-moon and not gravitationally bound to earth like a true satellite. It's orbit transfers between a Quasi satellite orbit type which resides in the L1 and L2 Lagrange points, and Horseshoe orbit between the L4 and L5 Lagrange points.[15][25]
In a rotating frame of reference Kamoʻoalewa appears to circle elliptically around the Earth every ~45 years.[26] Although it is too distant to be considered a true natural satellite of Earth, it is the best and most stable example to date of a near-Earth companion, or quasi-satellite.[3] Orbital and Yarkovsky effect modeling suggest it will be stable for 0.3-0.5 million years.[19][18][25]
Paul Chodas, manager of NASA's Center for Near-Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory (JPL) in Pasadena, California described the orbit of 2016 HO3 as a quasi-satellite of Earth. Unlike asteroid 2003 YN107, which previously followed a similar orbit, 2016 HO3 is more stable and has been Earth's companion for more than a century and will remain so for much longer. This asteroid spends half of its orbit closer to the Sun than Earth and the other half farther away, causing it to oscillate above and below Earth's orbit annually. Its orbit experiences slight drifts that Earth's gravity corrects, keeping it between 38 and 100 times the distance of the Moon. Thus, 2016 HO3 continually dances around the Earth.[4]
The closest Earth approach was on 27 December 1923 (101 years ago) (1923-12-27) at 12.44 million km (0.0832 AU; 32.4 LD).[2] By late May 2369, the asteroid will be 2.0 AU (780 LD; 300 million km) from Earth.[27] The Earth-like orbit may be a result of it being lunar ejecta.[13] Most objects in this kind of orbit are eventually perturbed out of being in an Earth-co-orbital state and hit the Earth, Venus, or the Sun or are ejected from the solar system, and Kamoʻoalewa will probably hit the Earth in the next 100 million years.[16]
Physical characteristics
The size of Kamoʻoalewa has not yet been firmly established, but it is approximately 40–100 m (130–330 ft).[4] Based on an assumed standard albedo for stony S-type asteroids of 0.20, its absolute magnitude of 24.3 corresponds to a 41 meters (135 ft) diameter.[5]
Photometric observations in April 2017 revealed that Kamoʻoalewa is a fast rotator. Lightcurve analysis gave a rotation period of 0.467 ± 0.008 hours (28.02 ± 0.48 minutes) and a brightness variation of 0.80±0.05magnitude (U=2).[5][b]. 2024 inversion modeling was used to create a 100m x 81m x 46m (~72m diameter) 3D model from light curve data.[28]
Lunar ejecta modeling shows some avenues that can achieve a stable QS 469219 Kamo’oalewa-style orbit.[29][15][16]
Exploration
Proposed missions
De la Fuente Marcos & de la Fuente Marcos first suggested in situ study of 2016 HO3 because of its ideal orbital characteristics in their August 2016 paper.[30]
During the 2017 Astrodynamics Specialist Conference held in Stevenson in the U.S. state of Washington, a team composed of graduate research assistants from the University of Colorado Boulder and the São Paulo State University (UNESP) was awarded for presenting a project denominated "Near-Earth Asteroid Characterization and Observation (NEACO) Mission to Asteroid (469219) 2016 HO3", providing the first baselines for the investigation of this celestial object using a spacecraft.[31][32][33] Recently, another version of this work was presented adopting different constraints in the dynamics.[34]
A 2019 NASA solar sail mission proposal selected it as a target.[7]
524522 Zoozve, a quasi-satellite of Venus, and the first quasi-satellite discovered around any major planet
Notes
^Computed with JPL Horizons using a geocentric solution. Ephemeris Type: Orbital Elements / Center: 500 / Time Span: 2022-Jan-21 (to match infobox epoch)
^ abExceptional rotation period of 0.467 ± 0.008 hours (28.02 ± 0.48 minutes) with a brightness amplitude of 0.80±0.05 mag, quality code = 2, based on summary figures at the LCDB, which references (Reddy 2018).[5] Relevant abstract in ADS is (Reddy 2017).[38]
^ abHeiligers, J., Fernandez, J. M., Stohlman, O. R., & Wilkie, W. K. (2019). Trajectory design for a solar-sail mission to asteroid 2016 HO3. Astrodynamics, 3(3), 231-246. https://doi.org/10.1007/s42064-019-0061-1
^Venigalla, C., Baresi, N., Aziz, J. D., Bercovici, B., Brack, D. N., Dahir, A., De Smet, S., Fulton, J., Pellegrino, M. M., & Van wal, S. (2019). Near-Earth Asteroid Characterization and Observation (NEACO) Mission to Asteroid (469219) 2016 HO3. Journal of Spacecraft and Rockets, 56(4), 1121-1136. https://doi.org/10.2514/1.A34268
^Jin, W., Li, F., Yan, J., Yang, X., Ye, M., Andert, T., & Peytavi, G. (2019). Simulation of global GM estimate of Asteroid (469219) 2016 HO3 for China’s future asteroid mission EPSC-DPS, Geneva, CH
^Yan, J., Liu, L., Ye, M., Jin, W., Qiu, D., & Barriot, J.-P. (2022). A simulation of the joint estimation of the GM value and the ephemeris of the asteroid 2016 HO3. Icarus, 385. https://doi.org/10.1016/j.icarus.2022.115120
^Zhang, X., Luo, Y., Xiao, Y., Liu, D., Guo, F., & Guo, Q. (2021). Developing Prototype Simulants for Surface Materials and Morphology of Near Earth Asteroid 2016 HO3. Space: Science & Technology, 2021. https://doi.org/10.34133/2021/9874929
^ abcdCastro-Cisneros, J. D., Malhotra, R., & Rosengren, A. J. (2023). Lunar ejecta origin of near-Earth asteroid Kamo'oalewa is compatible with rare orbital pathways. Commun Earth Environ, 4(1), 372. https://doi.org/10.1038/s43247-023-01031-w
^ abReddy, V., Kuhn, O., Thirouin, A., Conrad, A., Malhotra, R., Sanchez, J., & Veillet, C. (2017). Ground-based Characterization of Earth Quasi Satellite (469219) 2016 HO3 49th AAS-DPS Meeting, https://ui.adsabs.harvard.edu/abs/2017DPS....4920407R/abstract
^ abcFenucci, M., & Novaković, B. (2021). The Role of the Yarkovsky Effect in the Long-term Dynamics of Asteroid (469219) Kamo’oalewa. The Astronomical Journal, 162(6). https://doi.org/10.3847/1538-3881/ac2902
^ abDermawan, B. (2019). Temporal Earth Coorbital Types of Asteroid 2016 HO3. Paper No. 012038 6th International Conference on Mathematics & Natural Sciences 2019. IOP Publishing. DOI: 10.1088/1742-6596/1127/1/012038
^Ren, J., Wu, B., Hesse, M. A., Li, H., Liu, Y., & Wang, X. (2024). Surface dynamics of small fast-rotating asteroids: Analysis of possible regolith on asteroid 2016 HO3. Astronomy & Astrophysics, 692. https://doi.org/10.1051/0004-6361/202451407
^C. de la Fuente Marcos & R. de la Fuente Marcos. (2016).Asteroid (469219) 2016 HO3, the smallest and closest Earth quasi-satellite. Monthly Notices of the Royal Astronomical Society 2016 Vol. 462 Issue 4 Pages 1-16 DOI: 10.1093/mnras/stw1972