2001 QR322

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. ↑ 1.0 1.1 1.2 "JPL Small-Body Database Browser: (2001 QR322)" (2008-07-21 last obs). Retrieved 2009-09-04.
    2. ↑ 2.0 2.1 2.2 "List Of Neptune Trojans". Minor Planet Center. Retrieved 2011-05-08.
    3. ↑ 3.0 3.1 "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. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 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 2012-03-20.

    External links