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
- ↑ 1.0 1.1 1.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Lua error in package.lua at line 80: module 'strict' not found.
External links
- Orbital simulation from JPL (Java)
- Ephemeris
