// Workers AI · dad joke modeWhat did 164207 Cardea say to its date? You're a star.

164207 Cardea
	Cardea photographed by the Canada–France–Hawaii Telescope in February 2007
Discovery
Discovered by	LINEAR
Discovery site	Lincoln Lab's ETS
Discovery date	13 April 2004
Designations
Pronunciation	/ˈkɑːrdiə/
Named after	Cardea
Alternative designations	2004 GU9
Minor planet category	NEO · Apollo
Orbital characteristics
	Epoch 21 November 2025 (JD 2461000.5)
	Uncertainty parameter 0
Observation arc	8688 days (23.79 yr)
Aphelion	1.1372 AU (170.12 Gm)
Perihelion	0.8650 AU (129.40 Gm)
Semi-major axis	1.0011 AU (149.76 Gm)
Eccentricity	0.1359
Orbital period (sidereal)	1.0017 yr (365.87 d)
Mean anomaly	97.3298°
Mean motion	0° 59m 1.464s / day
Inclination	13.6529°
Longitude of ascending node	38.3866°
Longitude of perihelion	280.55672±0.00007°
Time of perihelion	2456145.53817±0.00006 jd
Argument of perihelion	279.3410°
Earth MOID	0.0031 AU (460,000 km)
Physical characteristics
Mean diameter	163 m
Geometric albedo	0.219
Absolute magnitude (H)	21.1

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 $\sigma =\lambda -\lambda _{p}$ ^[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 $\sigma$ 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.^[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

Notes

↑ Where $\lambda$ and $\lambda _{p}$ are the mean longitudes of Cardea and Earth, respectively

References

1 2 3 "(164207) = 2004 GU9". Minor Planet Center. Retrieved 3 June 2024.
1 2 3 4 "164207 Cardea (2004 GU9)". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 2164207. Retrieved 1 November 2025.
1 2 3 4 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.
1 2 3 4 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.
↑ "Major News about Minor Objects: Risk monitoring". hohmanntransfer. 14 April 2004. Archived from the original on 6 November 2020. Retrieved 2 March 2015.
↑ "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 1 March 2015.
↑ "Competition Announced to Name a Quasi-Moon". IAU. 31 May 2024. Retrieved 3 June 2024.
↑ "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).
↑ Wall, Mike (2 December 2024). "Strange "quasi-moon" of Earth will get one of these 7 names". Space.com. Retrieved 13 January 2025.
↑ "WGSBN Bulletin Volume 5, #1" (PDF). WGSBN Bulletin. 5 (1). International Astronomical Union: 28. 13 January 2025. Retrieved 13 January 2025.
↑ "NEO Groups". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 February 2002. Retrieved 4 June 2012.
↑ 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.

External links

Dynamical evolution of Earth’s quasi-satellites: 2004 GU9 and 2006 FV35 by Wajer, P. 2010, Icarus, Volume 209, Issue 2, pp. 488–493.
164207 Cardea at NeoDyS-2, Near Earth Objects—Dynamic Site
- Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
164207 Cardea at ESA–space situational awareness
- Ephemerides · Observations · Orbit · Physical properties · Summary
164207 Cardea at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

[12] Where $\lambda$ and $\lambda _{p}$ are the mean longitudes of Cardea and Earth, respectively

[MPC-object-1] 1 2 3 "(164207) = 2004 GU9". Minor Planet Center. Retrieved 3 June 2024.

[JPL-2] 1 2 3 4 "164207 Cardea (2004 GU9)". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 2164207. Retrieved 1 November 2025.

[Marcos2014-3] 1 2 3 4 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.

[Wajer2010-4] 1 2 3 4 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.

[hohmanntransfer-5] "Major News about Minor Objects: Risk monitoring". hohmanntransfer. 14 April 2004. Archived from the original on 6 November 2020. Retrieved 2 March 2015.

[removed-6] "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 1 March 2015.

[IAU-20240531-7] "Competition Announced to Name a Quasi-Moon". IAU. 31 May 2024. Retrieved 3 June 2024.

[namingcontest-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).

[namefinalists-9] Wall, Mike (2 December 2024). "Strange "quasi-moon" of Earth will get one of these 7 names". Space.com. Retrieved 13 January 2025.

[WGSBN-V5-1-10] "WGSBN Bulletin Volume 5, #1" (PDF). WGSBN Bulletin. 5 (1). International Astronomical Union: 28. 13 January 2025. Retrieved 13 January 2025.

[NEO-groups-11] "NEO Groups". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 February 2002. Retrieved 4 June 2012.

[TPS20240521-13] 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.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[a]

[12]

This page was redesigned at the edge.

A page that knows where it met you.