  Trans-Neptunian objects (TNOs) are icy/rocky bodies that move beyond the
orbit of Neptune in a region known as the trans-Neptunian belt (or
Edgeworth-Kuiper belt). In contrast to the predictions of accretion models that
feature protoplanetary disk planetesimals evolving on dynamically cold orbits
(with both very small eccentricities, e, and inclinations, i), in reality TNOs
exhibit surprisingly wide ranges of orbital eccentricities and inclinations.
Several theoretical models have addressed the origin and orbital evolution of
the main dynamical classes of TNOs, but none have successfully reproduced them
all. In addition, none have explained several objects on peculiar orbits, or
provided insightful predictions, without which a model cannot be tested
properly against observations. Based on extensive simulations of planetesimal
disks with the presence of the four giant planets and huge numbers of modeled
planetesimals, I explore in detail the dynamics of the TNOs, in particular
their (un)stable regions over timescales comparable to the age of the solar
system, and the role of resonances across the entire trans-Neptunian region. I
also propose that, along with the orbital history of the giant planets, the
orbital evolution of primordial embryos (massive planetesimals comparable to
Mars-Earth masses) can explain the fine orbital structure of the
trans-Neptunian belt, the orbits of Jovian and Neptunian Trojans, and possibly
the current orbits of the giant planets. Those primordial embryos were
ultimately scattered by the giant planets, a process that stirred both the
orbits of the giant planets and the primordial planetesimal disk to the levels
observed at 40-50 AU. In particular, the main constraints provided by the
trans-Neptunian belt are optimally satisfied if at least one such primordial
embryo (planetoid) survived in the outskirts of the solar system.

Earth and Planetary Astrophysics