J. Horner, P. S. Lykawka, M. T. Bannister, P. Francis
The recent discovery of the first Neptune Trojan at the planet's trailing
(L5) Lagrange point, 2008 LC18, offers an opportunity to confirm the formation
mechanism of a member of this important tracer population for the Solar
system's dynamical history. We tested the stability of 2008 LC18's orbit
through a detailed dynamical study, using test particles spread across the
\pm3{\sigma} range of orbital uncertainties in a, e, i and {\Omega}. This
showed that the wide uncertainties of the published orbit span regions of both
extreme dynamical instability, with lifetimes < 100 Myr, and with significant
stability (> 1 Gyr lifetimes). The stability of 2008 LC18's clones is greatly
dependent on their semi-major axis and only weakly correlated with their
eccentricity. Test particles on orbits with an initial semi-major axis less
than 29.91 AU have dynamical half-lives shorter than 100 Myr; in contrast,
particles with an initial semi-major axis greater than 29.91 AU exhibit such
strong dynamical stability that almost all are retained over the 1 Gyr of our
simulations. More observations of this object are necessary to improve the
orbit. If 2008 LC18 is in the unstable region, then our simulations imply that
it is either a temporary Trojan capture, or a representative of a slowly
decaying Trojan population (like its sibling the L4 Neptunian Trojan 2001
QR322), and that it may not be primordial. Alternatively, if the orbit falls
into the larger, stable region, then 2008 LC18 is a primordial member of the
highly stable and highly inclined component of the Neptune Trojan population,
joining 2005 TN53 and 2007 VL305. We attempted to recover 2008 LC18 using the
2.3 m telescope at Siding Spring Observatory to provide this astrometry, but
were unsuccessful due to the high stellar density of its current sky location
near the galactic centre. The recovery of this object will require a telescope
in the 8m class.
View original:
http://arxiv.org/abs/1202.3279
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