164207 Cardea
Sub-kilometer asteroid and quasi-satellite of Earth
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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]
Cardea photographed by the Canada–France–Hawaii Telescope in February 2007 | |
| Discovery[1] | |
|---|---|
| Discovered by | LINEAR |
| Discovery site | Lincoln Lab's ETS |
| Discovery date | 13 April 2004 |
| Designations | |
| (164207) Cardea | |
| Pronunciation | /ˈkɑːrdiə/ |
Named after | Cardea |
| 2004 GU9 | |
| NEO · Apollo | |
| Orbital characteristics[2] | |
| 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) |
| 1.0011 AU (149.76 Gm) | |
| Eccentricity | 0.1359 |
| 1.0017 yr (365.87 d) | |
| 97.3298° | |
| 0° 59m 1.464s / day | |
| Inclination | 13.6529° |
| 38.3866° | |
| 280.55672±0.00007° | |
| 2456145.53817±0.00006 jd | |
| 279.3410° | |
| Earth MOID | 0.0031 AU (460,000 km) |
| Physical characteristics | |
| 163 m[3]: 2988 | |
| 0.219[3]: 2988 | |
| 21.1[2] | |
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 [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
See also
- (277810) 2006 FV35, another quasi-satellite of Earth
Notes
- Where and are the mean longitudes of Cardea and Earth, respectively
