(612243) 2001 QR322
| Discovery | |
|---|---|
| Discovered by | Deep Ecliptic Survey |
| Discovery date | 21 August 2001[1] |
| Designations | |
| MPO157352 | |
| Neptune trojan | |
| Orbital characteristics[1][2] | |
| Epoch 2011-Aug-27.0 (JD 2455800.5) | |
| Aphelion | 31.326 AU |
| Perihelion | 29.468 AU |
| 30.397 AU | |
| Eccentricity | 0.0306 |
| 167.59 yr (61212 d) | |
| 56.8° | |
| Inclination | 1.3213° |
| 151.55° | |
| 168.1° | |
| Physical characteristics | |
| Dimensions | 60–160 km[3] |
| 8.2 | |
2001 QR322 (also written 2001 QR322) was the first Neptune trojan discovered, in 2001 by the Deep Ecliptic Survey. It orbits ahead of Neptune at its L4 Lagrangian point.[2][4]
With an absolute magnitude of 7.8[1] to 8.2,[2] it has a diameter in the range of 60 to 160 km.[3]
Other Neptune trojans have been discovered since. A study by Scott S. Sheppard and Chad Trujillo from the Carnegie Institution suggests that Neptune could possibly have twenty times more trojans than Jupiter.[5]
Dynamical stability
Early studies of the dynamical stability of 2001 QR322, which used a small number of test particles spread over the uncertainties of just a few orbital parameters that were derived from a limited observation arc, suggested that 2001 QR322 is on a remarkably stable orbit, because most test particles remained on trojan orbits for 5 Gyr.[6] Thereafter, the stability of Neptune trojans was simply assumed.[6]
A more recent study, which used a very large number of test particles spread over the 3σ uncertainties in all six orbital parameters derived from a longer observational arc, has indicated that 2001 QR322 is far less dynamically stable than previously thought.[6] The test particles were lost exponentially with a half life of 553 Myr.[6] Further observations can determine whether 2001 QR322's orbit is actually within the dynamically stable or within the unstable part.[6]
The stability is strongly dependent on semi-major axis, with a≥30.30 AU being far less stable, but only very weakly dependent on the other orbital parameters.[6] This is because those with larger semi-major axes have larger libration amplitudes, with amplitudes ~70° and above being destabilized by secondary resonances between the trojan motion and the dynamics of at least Saturn, Uranus, and Neptune.[6] Secular resonances were found not to contribute to the dynamical stability of 2001 QR322.[6]
References
- ^ a b c "JPL Small-Body Database Browser: (2001 QR322)" (2008-07-21 last obs). Retrieved 4 September 2009.
- ^ a b c "List Of Neptune Trojans". Minor Planet Center. Retrieved 8 May 2011.
- ^ a b "Absolute Magnitude (H)". Archived from the original on 14 May 2008. Retrieved 8 May 2008.
{{cite web}}: Unknown parameter|deadurl=ignored (|url-status=suggested) (help) - ^ Marc W. Buie. "Orbit Fit and Astrometric record for 01QR322" (2008-07-21 using 26 of 26 observations). SwRI (Space Science Department). Retrieved 3 September 2009.
- ^ "Neptune May Have Thousands of Escorts". Space.com. 30 January 2007. Retrieved 4 September 2009.
- ^ a b c d e f g h Horner, J.; Lykawka, P. S. (June 2010). "2001 QR322: a dynamically unstable Neptune Trojan?" (pdf). Monthly Notices of the Royal Astronomical Society. 405 (1): 49–56. arXiv:1002.4699. Bibcode:2010MNRAS.405...49H. doi:10.1111/j.1365-2966.2010.16441.x. Retrieved 20 March 2012.
{{cite journal}}: CS1 maint: unflagged free DOI (link)
External links
- Orbital simulation from JPL (Java)
- Ephemeris