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164207 Cardea

164207 Cardea
Cardea photographed by the Canada–France–Hawaii Telescope in February 2007
Discovery[1]
Discovered byLINEAR
Discovery siteLincoln Lab's ETS
Discovery date13 April 2004
Designations
Pronunciation/ˈkɑːrdiə/
Named after
Cardea
2004 GU9
NEO · Apollo
Orbital characteristics[2]
Epoch 21 November 2025 (JD 2461000.5)
Uncertainty parameter 0
Observation arc8688 days (23.79 yr)
Aphelion1.1372 AU (170.12 Gm)
Perihelion0.8650 AU (129.40 Gm)
1.0011 AU (149.76 Gm)
Eccentricity0.1359
1.0017 yr (365.87 d)
97.3298°
0° 59m 1.464s / day
Inclination13.6529°
38.3866°
280.55672±0.00007°
2456145.53817±0.00006 jd
279.3410°
Earth MOID0.0031 AU (460,000 km)
Physical characteristics
163 m[3]: 2988 
0.219[3]: 2988 
21.1[2]

164207 Cardea (provisional designation 2004 GU9) is a sub-kilometer asteroid, classified as a near-Earth object and potentially hazardous asteroid of the Apollo group. It is a quasi-satellite of Earth, a situation that should persist until around 2600, when it is expected to shift to a regular horseshoe orbit for a few thousand years.[4]

On 14 April 2004 (with less than a 1-day observation arc), the Sentry Risk Table showed 180 virtual impactors.[5] It was removed from the Sentry Risk Table 2 days later on 16 April 2004.[6] As later precovery observations by Haleakala-AMOS from 2001 have been found, Cardea now has a well determined orbit with an observation arc of 24 years.[1]

Discovery and naming

This asteroid was discovered on 13 April 2004 by the Lincoln Near-Earth Asteroid Research (LINEAR) project near Socorro, New Mexico and given the provisional designation 2004 GU9.[1] Following the naming of 524522 Zoozve, a quasi-satellite of Venus, Radiolab and the International Astronomical Union held a public naming campaign for this quasi-satellite from June to September 2024.[7][8] Seven finalist names were revealed in December 2024, with the names being Bakunawa, Cardea, Ehaema, Enkidu, Ótr, Tarriaksuk, and Tecciztecatl.[9] The winning name was Cardea, the Roman goddess of hinges. The name was announced by the International Astronomical Union on 13 January 2025.[10]

Orbit

Cardea orbits the Sun with a semi-major axis of 1.001 astronomical units (AU), taking 365.87 days to complete one orbit. It is classified as a near-Earth asteroid (NEA) and an Apollo asteroid;[2] Apollo asteroids are NEAs that cross Earth's orbit but have semi-major axes above 1 AU.[11] Its orbit is inclined by 13.653° with respect to the ecliptic plane. Along its orbit, its distance from the Sun varies from 0.865 AU at perihelion to 1.137 AU at aphelion due to its moderate[3]: 2987  orbital eccentricity of 0.136.[2]

Cardea is in a 1:1 mean-motion resonance with Earth, and it currently orbits in a quasi-satellite configuration.[4]: 489  Quasi-satellites have principal libration angles [a] that librate around 0°,[4]: 488  appearing to distantly orbit Earth from its perspective despite directly orbiting the Sun. All Earth quasi-satellites are temporary;[12] Cardea has been a quasi-satellite for about 600 years, and will eventually lose its status as one in about 500 years. Perturbations from Venus play a role in destabilizing Cardea from its quasi-satellite configuration even though their orbits do not cross. Currently, the libration of Cardea's has an amplitude of 8–10°, with a libration period of 70 years. After exiting its quasi-satellite phase, it will enter a horseshoe configuration.[4]: 490–491 

Physical characteristics

Cardea has a diameter of 163 metres (535 ft) and an albedo of 0.219.[3]: 2988 

Animation of 164207 Cardea's orbit from 1600 to 2500
Relative to Sun and Earth
Around Earth
Around Sun
   Sun ·    Earth ·   Cardea

See also

Notes

  1. ^ Where and are the mean longitudes of Cardea and Earth, respectively

References

  1. ^ a b c "(164207) = 2004 GU9". Minor Planet Center. Retrieved 3 June 2024.
  2. ^ a b c d "164207 Cardea (2004 GU9)". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 2164207. Retrieved 1 November 2025.
  3. ^ a b c d de la Fuente Marcos, C.; de la Fuente Marcos, R. (21 October 2014). "Asteroid 2014 OL339: yet another Earth quasi-satellite". Monthly Notices of the Royal Astronomical Society. 445 (3): 2985–2994. arXiv:1409.5588. Bibcode:2014MNRAS.445.2961D. doi:10.1093/mnras/stu1978.
  4. ^ a b c d Wajer, Paweł (October 2010). "Dynamical evolution of Earth's quasi-satellites: 2004 GU9 and 2006 FV35". Icarus. 209 (2): 488–493. Bibcode:2010Icar..209..488W. doi:10.1016/j.icarus.2010.05.012.
  5. ^ "Major News about Minor Objects: Risk monitoring". hohmanntransfer. 14 April 2004. Archived from the original on 6 November 2020. Retrieved 2 March 2015.
  6. ^ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 1 March 2015.
  7. ^ "Competition Announced to Name a Quasi-Moon". IAU. 31 May 2024. Retrieved 3 June 2024.
  8. ^ "OFFICIAL RULES: Name a Quasi Moon!". Radiolab. Retrieved 3 June 2024. Radiolab is partnering with the International Astronomical Union to launch a months-long global naming contest for one of Earth's quasi-moons (asteroid 164207).
  9. ^ Wall, Mike (2 December 2024). "Strange "quasi-moon" of Earth will get one of these 7 names". Space.com. Retrieved 13 January 2025.
  10. ^ "WGSBN Bulletin Volume 5, #1" (PDF). WGSBN Bulletin. 5 (1). International Astronomical Union: 28. 13 January 2025. Retrieved 13 January 2025.
  11. ^ "NEO Groups". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 February 2002. Retrieved 4 June 2012.
  12. ^ Stahl, Asa (21 May 2024). "Earth's quasi-moons, minimoons, and ghost moons". The Planetary Society. Archived from the original on 2 October 2025. Retrieved 3 October 2025.

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