(309239) 2007 RW10
|Discovery date||September 9, 2007|
|Minor planet category||trans-Neptunian object|
|Epoch September 30, 2012 (JD 2456200.5)|
|Semi-major axis||30.32255 AU|
|Orbital period||166.98 yr|
|Longitude of ascending node||187.03214°|
|Argument of perihelion||96.73413°|
|Absolute magnitude (H)||6.5|
(309239) 2007 RW10, also written (309239) 2007 RW10, is a temporary quasi-satellite of Neptune. Observed from Neptune, it would appear to go around it during one Neptunian year but it actually orbits the Sun, not Neptune.
Discovery, orbit and physical properties 
(309239) 2007 RW10 was discovered by the Palomar Distant Solar System Survey on September 9, 2007. At the time of discovery, this minor body was believed to be a Neptune trojan, but it is no longer listed as such. The Jet Propulsion Laboratory classifies (309239) 2007 RW10 as trans-Neptunian object but the Minor Planet Center includes the object among Centaurs. It moves in an orbit with an inclination of 36.1º, a semi-major axis of 30.32 AU, and an eccentricity of 0.2996. Herschel-PACS observations indicate that it has a diameter of 247 km.
Quasi-satellite dynamical state and orbital evolution 
(309239) 2007 RW10 is currently following a quasi-satellite loop around Neptune. The object has been a quasi-satellite of Neptune for about 12,500 years and it will remain in that dynamical state for another 12,500 years. Prior to the quasi-satellite dynamical state, (309239) 2007 RW10 was an L5 Trojan and it will come back to that state soon after leaving its current quasi-satellite path. Its orbital inclination is the largest among known Neptune co-orbitals. It is also the largest known object trapped in the 1:1 mean motion resonance with any major planet.
(309239) 2007 RW10 is a dynamically hot (both, high eccentricity and inclination) object that is unlikely to be a primordial Neptune co-orbital. It probably originated well beyond Neptune and was later temporarily captured in the 1:1 commensurability with Neptune.
See also 
- The trans-Neptunian object 2005 TN74 was also suspected of being a Neptune trojan at the time of discovery.
- "JPL Small-Body Database Browser: 2007 RW10". Retrieved 2012-07-24.
- Santos-Sanz, P., Lellouch, E., Fornasier, S., Kiss, C., Pal, A., Müller, T. G., Vilenius, E., Stansberry, J., Mommert, M., Delsanti, A., Mueller, M., Peixinho, N., Henry, F., Ortiz, J. L., Thirouin, A., Protopapa, S., Duffard, R., Szalai, N., Lim, T., Ejeta, C., Hartogh, P., Harris, A. W., & Rengel, M. (2012). “TNOs are Cool”: A Survey of the Transneptunian Region IV - Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel Space Observatory-PACS
- de la Fuente Marcos & de la Fuente Marcos (2012). "(309239) 2007 RW10: a large temporary quasi-satellite of Neptune". Astronomy and Astrophysics Letters 545: L9. arXiv:1209.1577. Bibcode:2012A%26A...545L...9D. doi:10.1051/0004-6361/201219931.
- "Discovery MPEC". Retrieved 2012-07-26.
- "Schwamb et al. 2010". Retrieved 2012-07-26.
- "Distant EKOs, 55". Retrieved 2012-07-24.
- "Distant EKOs 56". Retrieved 2012-07-24.
- Minor Planet Center List Of Neptune Trojans (2007-12-01)
- Horner, J., Lykawka, P. S., Bannister, M. T., & Francis, P. 2012 2008 LC18: a potentially unstable Neptune Trojan Monthly Notices of the Royal Astronomical Society, Volume 422, pp. 2145-2151
- Orbital simulation from JPL (Java) / Ephemeris
- MPEC 2007-X06 : 2007 RW10, 2007 RG283, 2007 RH283 (2007 Dec. 1)
- 2007 RW10 Precovery Images