2001 QR322

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2001 QR322
Discovered by Deep Ecliptic Survey
Discovery date 21 August 2001[1]
Neptune trojan
Orbital characteristics[1][2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 3
Observation arc 2605 days (7.13 yr)
Aphelion 30.955 AU (4.6308 Tm)
Perihelion 29.338 AU (4.3889 Tm)
30.147 AU (4.5099 Tm)
Eccentricity 0.026820
165.53 yr (60458.2 d)
0° 0m 21.436s /day
Inclination 1.3241°
Earth MOID 28.3211 AU (4.23678 Tm)
Jupiter MOID 24.1875 AU (3.61840 Tm)
Physical characteristics
Dimensions 60–160 km[3]

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[edit]

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]


  1. ^ a b c "JPL Small-Body Database Browser: (2001 QR322)" (2008-07-21 last obs). Retrieved 30 March 2016. 
  2. ^ a b c "List Of Neptune Trojans". Minor Planet Center. Retrieved 2011-05-08. 
  3. ^ a b "Absolute Magnitude (H)". Archived from the original on 14 May 2008. Retrieved 2008-05-08. 
  4. ^ Marc W. Buie. "Orbit Fit and Astrometric record for 01QR322" (2008-07-21 using 26 of 26 observations). SwRI (Space Science Department). Retrieved 2009-09-03. 
  5. ^ "Neptune May Have Thousands of Escorts". Space.com. 30 January 2007. Retrieved 2009-09-04. 
  6. ^ 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:1002.4699Freely accessible. Bibcode:2010MNRAS.405...49H. doi:10.1111/j.1365-2966.2010.16441.x. Retrieved 2012-03-20. 

External links[edit]