Astronomy:164207 Cardea

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164207 Cardea
File:2004 GU9 CFHT 2007-02-09 annotated.gif
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
(164207) Cardea
Pronunciation/ˈkɑːrdiə/
Named afterCardea
2004 GU9
Minor planet categoryNEO · Apollo
Orbital characteristics[2]
Epoch 21 November 2025 (JD 2461000.5)
Uncertainty parameter 0
Observation arc8688 days (23.79 yr)
|{{{apsis}}}|helion}}1.1372 astronomical unit|AU (170.12 Gm)
|{{{apsis}}}|helion}}0.8650 AU (129.40 Gm)
1.0011 AU (149.76 Gm)
Eccentricity0.1359
Orbital period1.0017 yr (365.87 d)
Mean anomaly97.3298°
Mean motion0° 59m 1.464s / day
Inclination13.6529°
Longitude of ascending node38.3866°
280.55672±0.00007°
|{{{apsis}}}|helion}}2456145.53817±0.00006 jd
279.3410°
Earth MOID0.0031 AU (460,000 km)
Physical characteristics
Mean diameter163 m[3]: 2988 
Geometric albedo0.219[3]: 2988 
Absolute magnitude (H)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 the hinge. 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 σ=λ−λp[lower-alpha 1] 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 σ 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 λ and λp are the mean longitudes of Cardea and Earth, respectively

References

  1. ↑ 1.0 1.1 1.2 "(164207) = 2004 GU9". Minor Planet Center. https://www.minorplanetcenter.net/db_search/show_object?object_id=164207. Retrieved 3 June 2024. 
  2. ↑ 2.0 2.1 2.2 2.3 "164207 Cardea (2004 GU9)". JPL Small-Body Database. Jet Propulsion Laboratory. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2164207. 
  3. ↑ 3.0 3.1 3.2 3.3 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. doi:10.1093/mnras/stu1978. Bibcode: 2014MNRAS.445.2961D. 
  4. ↑ 4.0 4.1 4.2 4.3 Wajer, Paweł (October 2010). "Dynamical evolution of Earth's quasi-satellites: 2004 GU9 and 2006 FV35". Icarus 209 (2): 488–493. doi:10.1016/j.icarus.2010.05.012. Bibcode: 2010Icar..209..488W. 
  5. ↑ "Major News about Minor Objects: Risk monitoring". hohmanntransfer. 2004-04-14. http://www.hohmanntransfer.com/mn/0404/14.htm#risks. 
  6. ↑ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. http://neo.jpl.nasa.gov/risk/removed.html. 
  7. ↑ "Competition Announced to Name a Quasi-Moon". IAU. 31 May 2024. https://iau.org/news/pressreleases/detail/iau2406/. 
  8. ↑ "OFFICIAL RULES: Name a Quasi Moon!". Radiolab. https://radiolab.org/moon-official-rules/. "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. https://www.space.com/the-universe/earth/strange-quasi-moon-of-earth-will-get-one-of-these-7-names. 
  10. ↑ "WGSBN Bulletin Volume 5, #1". WGSBN Bulletin (International Astronomical Union) 5 (1): 28. 13 January 2025. https://www.wgsbn-iau.org/files/Bulletins/V005/WGSBNBull_V005_001.pdf. Retrieved 13 January 2025. 
  11. ↑ "NEO Groups". NASA/JPL Near-Earth Object Program Office. http://neo.jpl.nasa.gov/neo/groups.html. 
  12. ↑ Stahl, Asa (21 May 2024). "Earth's quasi-moons, minimoons, and ghost moons". The Planetary Society. https://www.planetary.org/articles/the-quasi-moons-of-earth. 



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