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164207 Cardea

Sub-kilometer asteroid and quasi-satellite of Earth

Field	Value
minorplanet	yes
name	164207 Cardea
background	#FFC2E0
image	2004 GU9 CFHT 2007-02-09 annotated.gif
caption	Cardea photographed by the Canada–France–Hawaii Telescope in February 2007
discovery_ref
discoverer	LINEAR
discovery_site	Lincoln Lab's ETS
discovered	13 April 2004
mpc_name	(164207) Cardea
named_after	Cardea
pronounced
mp_category	NEOApollo
alt_names
orbit_ref
epoch	21 November 2025 (JD 2461000.5)
observation_arc	8688 days (23.79 yr)
uncertainty	0
aphelion	1.1372 AU
perihelion	0.8650 AU
semimajor	1.0011 AU
eccentricity	0.1359
period	1.0017 yr (365.87 d)
mean_motion	/ day
mean_anomaly	97.3298°
inclination	13.6529°
asc_node	38.3866°
long_periastron	°
time_periastron	jd
arg_peri	279.3410°
moid	0.0031 AU
mean_diameter	163 m
albedo	0.219
abs_magnitude	21.1

164207 Cardea (provisional designation ****) 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.

On 14 April 2004 (with less than a 1-day observation arc), the Sentry Risk Table showed 180 virtual impactors. It was removed from the Sentry Risk Table 2 days later on 16 April 2004.{{cite web |archive-url=https://web.archive.org/web/20020602101400/http://neo.jpl.nasa.gov/risk/removed.html |url-status=dead |archive-date=2002-06-02 |access-date=2015-03-01}} 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.

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 . 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. Seven finalist names were revealed in December 2024, with the names being Bakunawa, Cardea, Ehaema, Enkidu, Ótr, Tarriaksuk, and Tecciztecatl. The winning name was Cardea, the Roman goddess of the hinge. The name was announced by the International Astronomical Union on 13 January 2025.

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; Apollo asteroids are NEAs that cross Earth's orbit but have semi-major axes above 1 AU. 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 orbital eccentricity of 0.136.

Cardea is in a 1:1 mean-motion resonance with Earth, and it currently orbits in a quasi-satellite configuration. Quasi-satellites have principal libration angles \sigma = \lambda - \lambda_{p} that librate around 0°, appearing to distantly orbit Earth from its perspective despite directly orbiting the Sun. All Earth quasi-satellites are temporary; 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 \sigma 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.

Physical characteristics

Cardea has a diameter of 163 m and an albedo of 0.219.

Notes

References

|access-date=3 October 2025 |archive-date=2 October 2025 |archive-url=https://web.archive.org/web/20251002073229/https://www.planetary.org/articles/the-quasi-moons-of-earth |url-status=live

|doi-access=free

References

"164207 Cardea (2004 GU9)".
(2004-04-14). "Major News about Minor Objects: Risk monitoring". hohmanntransfer.
(31 May 2024). "Competition Announced to Name a Quasi-Moon". [[IAU]].
"OFFICIAL RULES: Name a Quasi Moon!". [[Radiolab]].
Wall, Mike. (2 December 2024). "Strange "quasi-moon" of Earth will get one of these 7 names". Space.com.
"NEO Groups". NASA/JPL Near-Earth Object Program Office.

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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