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469219 Kamoʻoalewa

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469219 Kamoʻoalewa (/kəˌmoʊʔoʊəˈlɛvə/),[6] provisionally designated 2016 HO3, is a very small asteroid, fast rotator and near-Earth object of the Apollo group, approximately 40–100 meters (130–330 feet) in diameter. At present it is a quasi-satellite of Earth, and currently the second-smallest, closest, and most stable known such quasi-satellite (after 2023 FW13). The asteroid was discovered by Pan-STARRS at Haleakala Observatory on 27 April 2016. It was named Kamoʻoalewa, a Hawaiian word that refers to an oscillating celestial object.[1][2] The object's Earth-like orbit and its composition of lunar-like silicates may be a result of it being lunar ejecta.[7][8]

469219 Kamoʻoalewa
Orbit of Kamoʻoalewa in the inner Solar System
Discovery [1]
Discovered byPan-STARRS
Discovery siteHaleakala Observatory
Discovery date27 April 2016
Designations
(469219) 2016 HO3
Pronunciation/kəˌmoʊʔoʊəˈlɛvə/
Hawaiian: [kəˈmoʔowəˈlɛvə]
Named after
Kamoʻoalewa
("the oscillating fragment")
2016 HO3
Orbital characteristics [2]
Epoch 2024-Mar-31 (JD 2460400.5)
Uncertainty parameter 0
Observation arc20.00 yr (7,306 d)
Aphelion1.10373 AU
Perihelion0.89816 AU
1.00094 AU
Eccentricity0.10269
(964 wrt Earth)[a]
1.0014 yr (365.77 d)
175.153°
0° 59m 3.192s / day
Inclination7.79605°
65.7907°
305.0478°
Earth MOID0.0311 AU (12.1 LD)
Physical characteristics
  • 0.041 km (calculated)[5]
  • 0.04–0.10 km[4]
0.467±0.008 h[b]
0.20 (assumed)[5]
S (assumed)[5]

Discovery and naming

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Kamoʻoalewa was first spotted on 27 April 2016, by the Pan-STARRS 1 asteroid survey telescope on Haleakalā, Hawaii, that is operated by the University of Hawaii's Institute for Astronomy and funded by NASA's Planetary Defense Coordination Office.[1][4] 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.[9][10] The official naming citation was published by the Minor Planet Center on 6 April 2019 (M.P.C. 112435).[11]

Orbit and classification

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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 since it is a quasi-satellite of Earth and will continue to be so for hundreds of years. Its orbit has an eccentricity of 0.10 and an inclination of 8° with respect to the ecliptic.[2] It presently has an Earth minimum orbital intersection distance of 0.031 AU (4.6 million km) that translates into 12 lunar distances.[2] This distance is well outside of Earth's Hill sphere of 1.5 million km (3.9 LD).

Quasi-satellite of Earth

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The oscillating path of asteroid Kamoʻoalewa as it orbits around the Sun. The traced path of Kamoʻoalewa makes it appear as a constant companion of the Earth.

In a frame of reference that rotates once a year, so that the Earth and the Sun remain relatively stationary, Kamoʻoalewa appears to circle elliptically around the Earth. The object is beyond the Hill sphere of Earth and the Sun exerts a much stronger pull on it than Earth does. 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]

Paul Chodas, manager of NASA's Center for Near-Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory (JPL) in Pasadena, California, commented on the orbit:

Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the Sun, we refer to it as a quasi-satellite of Earth. One other asteroid – 2003 YN107 – followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. This new asteroid is much more locked onto us. Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth's companion for centuries to come.[4]

In its yearly trek around the Sun, Kamoʻoalewa spends approximately half of the time closer to the Sun than Earth is (that is, the asteroid is inside the Earth's orbit) and passes ahead of our planet, and approximately half of the time farther away (crosses outside Earth's orbit), causing it to fall behind. Also, its orbit is tilted a little, causing it to bob up and then down once each year through Earth's orbital plane. In effect, this small asteroid is caught in a game of leap frog with Earth that will last for hundreds of years.[4]

Chodas explained how the asteroid's orbit also undergoes a slow, back-and-forth twist over multiple decades:

The asteroid's loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth's gravity is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon.[c] The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon. In effect, this small asteroid is caught in a little dance with Earth.[4]

Kamoʻoalewa is currently the most stable among the quasi-satellites of Earth that have been discovered and will remain in that orbit for about the next 300 years.[7] But it alternates between stages of being a quasi-satellite and of being in a horseshoe orbit.[12] In the 24th century it will go back to being in a horseshoe orbit. The closest Earth approach was on 27 December 1923 (100 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.[13] The Earth-like orbit may be a result of it being lunar ejecta.[7] After limiting crater size based on simulations of impacts that could eject a piece this large into a quasi-satellite orbit, and limiting crater age to between 1 and 10 million years based on the instability of the asteroid's orbit, a 2024 study found that the most likely origin is the 22 km (14 mi) wide Giordano Bruno crater.[8][12]

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.[12]

Physical characteristics

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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±0.05 magnitude (U=2).[5][b]

In 2021, a comprehensive physical characterization of Kamoʻoalewa was conducted using the Large Binocular Telescope and the Lowell Discovery Telescope, which found that the asteroid is composed of lunar-like silicates and may be an impact fragment from the Moon.[7][14]

Exploration

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Proposed missions

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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.[15][16][17] Recently, another version of this work was presented adopting different constraints in the dynamics.[18]

The China National Space Administration (CNSA) is planning a robotic mission that would return samples from Kamoʻoalewa.[19][20] This mission, Tianwen-2, is planned to launch in 2025.[21]

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Animation of the orbit of Kamoʻoalewa from 2000 to 2300, showing quasi-satellite phase
 
Relative to Sun and Earth (rotating frame of reference)
 
Around Earth (non-rotating frame)
 
Around Sun (non-rotating frame)
   Sun ·    Earth ·    469219 Kamo'oalewa
Animation of the orbit of Kamoʻoalewa from 1600 to 2500, going from horseshoe orbit to quasi-satellite and back
 
Relative to Sun and Earth (rotating frame of reference)
 
Around Earth (non-rotating frame)
 
Around Sun (non-rotating frame)
   Sun ·    Earth ·    469219 Kamo'oalewa

See also

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Notes

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  1. ^ Computed with JPL Horizons using a geocentric solution. Ephemeris Type: Orbital Elements / Center: 500 / Time Span: 2022-Jan-21 (to match infobox epoch)
  2. ^ a b Exceptional 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).[22]
  3. ^ For example on 2030-Jul-09, it will be 0.293 AU (114 LD) from Earth, but Earth's Hill sphere only has a radius of roughly 1.5 million km (3.9 LD). For comparison in 2022 Venus will be 103 LD from Earth.

References

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  1. ^ a b c d e "(469219) Kamoʻoalewa = 2016 HO3". Minor Planet Center. Retrieved 29 April 2024.
  2. ^ a b c d e f g "JPL Small-Body Database Browser: 469219 Kamo'oalewa (2016 HO3)" (2024-03-18 last obs.). Jet Propulsion Laboratory. Retrieved 29 April 2024.
  3. ^ a b de la Fuente Marcos, C.; de la Fuente Marcos, R. (November 2016). "Asteroid (469219) 2016 HO3, the smallest and closest Earth quasi-satellite". Monthly Notices of the Royal Astronomical Society. 462 (4): 3441–3456. arXiv:1608.01518. Bibcode:2016MNRAS.462.3441D. doi:10.1093/mnras/stw1972.
  4. ^ a b c d e f g Agle, DC; Brown, Dwayne; Cantillo, Laurie (15 June 2016). "Small Asteroid Is Earth's Constant Companion". Jet Propulsion Laboratory. Retrieved 29 April 2024.
  5. ^ a b c d e f g "LCDB Data for (469219)". MinorPlanet.Info — ALCDEF Query. Asteroid Lightcurve Database (LCDB). Retrieved 29 April 2024.
  6. ^ "He Noiʻi Nowelo i ka ʻIke Kuʻuna Hawaiʻi o ka ʻŌnaeao". imiloahawaii.org. ʻImiloa Astronomy Center. 30 December 2018. Retrieved 29 April 2024.
  7. ^ a b c d Sharkey, Ben; Reddy, Vishnu; Malhotra, Renu; et al. (11 November 2021). "Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa". Communications Earth & Environment. 2 (231). Nature: 231. arXiv:2111.06372. Bibcode:2021ComEE...2..231S. doi:10.1038/s43247-021-00303-7. S2CID 243985893.
  8. ^ a b Lea, Robert (23 April 2024). "Earth's weird 'quasi-moon' Kamo'oalewa is a fragment blasted out of big moon crater". Space.com. Retrieved 24 April 2024.
  9. ^ "A Hua He Inoa". ʻImiloa Astronomy Center. 30 December 2018.
  10. ^ ulukau HAWAIIAN ELECTRONIC LIBRARY
  11. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 29 April 2024.
  12. ^ a b c Jiao, Yifei; Cheng, Bin; et al. (19 April 2024). "Asteroid Kamo'oalewa's journey from the lunar Giordano Bruno crater to Earth 1:1 resonance". Nature Astronomy. 8 (7): 819–826. arXiv:2405.20411. Bibcode:2024NatAs.tmp...83J. doi:10.1038/s41550-024-02258-z.{{cite journal}}: CS1 maint: bibcode (link)
  13. ^ "Horizons Batch for May 2369 Geocentric distance". JPL Horizons. Retrieved 29 April 2024.
  14. ^ Devlin, Hannah (11 November 2021). "Near-Earth asteroid is a fragment from the moon, say scientists". The Guardian. Retrieved 29 April 2024.
  15. ^ Venigalla, C; Baresi, N; Aziz, J; Bercovici, B; Borderes Motta, G; Brack, D; Cardoso dos Santos, J; Dahir, A; Davis, A B; Smet, S D; et al. (2019). "Near-Earth Asteroid Characterization and Observation (NEACO) Mission to Asteroid (469219) 2016 HO3" (PDF). Journal of Spacecraft and Rockets. 56 (4): 1121–1136. Bibcode:2019JSpRo..56.1121V. doi:10.2514/1.A34268. S2CID 126452156. Retrieved 29 April 2024.
  16. ^ Venigala, C; et al. (September–October 2017). "STUDENT DESIGN COMPETITION" (PDF). Space Times Magazine. Retrieved 29 April 2024.
  17. ^ Cardoso dos Santos, J; Borderes Motta, G (March 2018). "Alunos da Unesp vencem competição internacional". UNESP Notícias (Portuguese). Retrieved 29 April 2024.
  18. ^ Venigalla, C; Baresi, N; Aziz, J; Bercovici, B; Brack, D; Dahir, A; Davis, A B; Smet, S D; et al. (February 2019). "Near-Earth Asteroid Characterization and Observation (NEACO) Mission to Asteroid (469219) 2016 HO3". Journal of Spacecraft and Rockets. 56 (4): 1121–1136. Bibcode:2019JSpRo..56.1121V. doi:10.2514/1.A34268. S2CID 126452156.
  19. ^ Gibney, Elizabeth (30 April 2019). "China plans mission to Earth's pet asteroid". Nature. doi:10.1038/d41586-019-01390-5. PMID 32346150. S2CID 155198626. Retrieved 29 April 2024.
  20. ^ Zhang, Xiaojing; Huang, Jiangchuan; Wang, Tong; Huo, Zhuoxi (18–22 March 2019). ZhengHe – A Mission to a Near-Earth Asteroid and a Main Belt Comet (PDF). 50th Lunar and Planetary Science Conference. Retrieved 29 April 2024.
  21. ^ Jones, Andrew (30 June 2021). "China outlines space plans to 2025". SpaceNews. Retrieved 29 April 2024.
  22. ^ Reddy, Vishnu; Kuhn, Olga; Thirouin, Audrey; et al. (October 2017). "Ground-based Characterization of Earth Quasi Satellite (469219) 2016 HO3". AAS DPS Meeting. 49. American Astronomical Society. id.204.07. Bibcode:2017DPS....4920407R.
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