We report the discovery and orbit of a new dwarf planet candidate, 2015 RR245, by the Outer Solar System Origins Survey (OSSOS). The orbit of 2015 RR245 is eccentric (e = 0.586), with a semimajor axis near 82 au, yielding a perihelion distance of 34 au. 2015 RR245 has g - r = 0.59 +/- 0.11 and absolute magnitude H-r = 3.6 +/- 0.1; for an assumed albedo of p(V) = 12%, the object has a diameter of similar to 670. km. Based on astrometric measurements from OSSOS and Pan-STARRS1, we find that 2015 RR245 is securely trapped on ten-megayear timescales in the 9: 2 mean-motion resonance with Neptune. It is the first trans-Neptunian object (TNO) identified in this resonance. On hundred-megayear. timescales, particles in 2015 RR245-like orbits depart and sometimes return to the resonance, indicating that 2015 RR245 likely forms part of the long-lived metastable population of distant TNOs that drift between resonance sticking and actively scattering via gravitational encounters with Neptune. The discovery of a 9: 2 TNO stresses the role of resonances in the long-term evolution of objects in the scattering disk. and reinforces the view that distant resonances are heavily populated in the current solar system. This object further motivates detailed modeling of the transient sticking population.

We report the discovery of the minor planet 2013 SY99 on an exceptionally distant, highly eccentric orbit. With a perihelion of 50.0. au, 2013 SY99' s orbit has a semimajor axis of 730 +/- 40. au, the largest known for a high-perihelion trans-Neptunian object (TNO), and well beyond those of (90377) Sedna and 2012 VP113. Yet, with an aphelion of 1420 +/- 90. au, 2013 SY99' s orbit is interior to the region influenced by Galactic tides. Such TNOs are not thought to be produced in the current known planetary architecture of the solar system, and they have informed the recent debate on the existence of a distant giant planet. Photometry from the Canada-France-Hawaii Telescope, Gemini North, and Subaru indicate 2013 SY99 is similar to 250. km in diameter and moderately red in color, similar to other dynamically excited TNOs. Our dynamical simulations show that Neptune's weak influence during 2013 SY99' s perihelia encounters drives diffusion in its semimajor axis of hundreds of astronomical units over 4. Gyr. The overall symmetry of random walks in the semimajor axis allows diffusion to populate 2013 SY99' s orbital parameter space from the 1000 to 2000. au inner fringe of the Oort cloud. Diffusion affects other known TNOs on orbits with perihelia of 45 to 49. au and semimajor axes beyond 250. au. This provides a formation mechanism that implies an extended population, gently cycling into and returning from the inner fringe of the Oort cloud.

abstract: Solar system orbital dynamics can offer unique challenges. Impacts of interplanetary dust particles can significantly alter the surfaces of icy satellites and minor planets. Impact heating from these particles can anneal away radiation damage to the crystalline structure of surface water ice. This effect is enhanced by gravitational focusing for giant planet satellites. In addition, impacts of interplanetary dust particles on the small satellites of the Pluto system can eject into the system significant amounts of secondary intra-satellite dust. This dust is primarily swept up by Pluto and Charon, and could explain the observed albedo features on Pluto's surface. In addition to Pluto, a large fraction of trans-neptunian objects (TNOs) are binary or multiple systems. The mutual orbits of these TNO binaries can range from very wide (periods of several years) to near-contact systems (less than a day period). No single formation mechanism can explain this distribution. However, if the systems generally formed wide, a combination of solar and body tides (commonly called Kozai Cycles-Tidal Friction, KCTF) can cause most systems to tighten sufficiently to explain the observed distributions. This KCTF process can also be used to describe the orbital evolution of a terrestrial-class exoplanet after being captured as a satellite of a habitable-zone giant exoplanet. The resulting exomoon would be both potentially habitable and potenially detectable in the full Kepler data set. / Dissertation/Thesis / Ph.D. Astrophysics 2013

The Pluto-Charon system has come into sharper focus following the flyby of New Horizons. We use N-body simulations to probe the unique dynamical history of this binary dwarf planet system. We follow the evolution of the debris disc that might have formed during the Charon-forming giant impact. First, we note that in situ formation of the four circumbinary moons is extremely difficult if Charon undergoes eccentric tidal evolution. We track collisions of disc debris with Charon, estimating that hundreds to hundreds of thousands of visible craters might arise from 0.3-5 km radius bodies. New Horizons data suggesting a dearth of these small craters may place constraints on the disc properties. While tidal heating will erase some of the cratering history, both tidal and radiogenic heating may also make it possible to differentiate disc debris craters from Kuiper belt object craters. We also track the debris ejected from the Pluto-Charon system into the Solar system; while most of this debris is ultimately lost from the Solar system, a few tens of 10-30 km radius bodies could survive as a Pluto-Charon collisional family. Most are plutinos in the 3: 2 resonance with Neptune, while a small number populate nearby resonances. We show that migration of the giant planets early in the Solar system's history would not destroy this collisional family. Finally, we suggest that identification of such a family would likely need to be based on composition as they show minimal clustering in relevant orbital parameters.

abstract: In this thesis I model the thermal and structural evolution of Kuiper Belt Objects (KBOs) and explore their ability to retain undifferentiated crusts of rock and ice over geologic timescales. Previous calculations by Desch et al. (2009) predicted that initially homogenous KBOs comparable in size to Charon (R ~ 600 km) have surfaces too cold to permit the separation of rock and ice, and should always retain thick (~ 85 km) crusts, despite the partial differentiation of rock and ice inside the body. The retention of a thermally insulating, undifferentiated crust is favorable to the maintenance of subsurface liquid and potentially cryovolcanism on the KBO surface. A potential objection to these models is that the dense crust of rock and ice overlying an ice mantle represents a gravitationally unstable configuration that should overturn by Rayleigh-Taylor (RT) instabilities. I have calculated the growth rate of RT instabilities at the ice-crust interface, including the effect of rock on the viscosity. I have identified a critical ice viscosity for the instability to grow significantly over the age of the solar system. I have calculated the viscosity as a function of temperature for conditions relevant to marginal instability. I find that RT instabilities on a Charon-sized KBO require temperatures T > 143 K. Including this effect in thermal evolution models of KBOs, I find that the undifferentiated crust on KBOs is thinner than previously calculated, only ~ 50 km. While thinner, this crustal thickness is still significant, representing ~ 25% of the KBO mass, and helps to maintain subsurface liquid throughout most of the KBO's history. / Dissertation/Thesis / M.S. Astrophysics 2013

Les petits corps du système solaire riches en volatiles incluent plusieurs populations d’objets : les astéroïdes de la ceinture principale, les astéroïdes troyens des planètes géantes, les objets trans-neptuniens (OTNs) et les comètes. Au cours de ces dernières années, l'’idée que leur position actuelle résulte de migrations orbitales plutôt qu’elle ne reflète leur région de formation a progressivement émergée. Spécifiquement, certains astéroïdes pourraient être des comètes, et certaines comètes pourraient être des OTNs. Je présente ici les travaux réalisés au cours de ma thèse pour contraindre la composition (minéralogie de surface et structure interne) de ces différentes populations afin i) de déterminer les liens qui les unissent, ii) comprendre leurs migrations passées et donc, iii) apporter de nouvelles contraintes aux modèles dynamiques décrivant la formation et l’évolution de notre système solaire. À cet effet, j’ai principalement utilisé comme méthode d’analyse l’observation spectroscopique, ainsi que la modélisation des données obtenues et leur comparaison aux données spectrales de météorites et poussières cosmiques étudiées en laboratoire. / The icy small bodies of our solar system encompass several populations of objects : the main belt asteroids, the giant planets Trojans, the Trans-Neptunian Objects (TNOs) and the comets. During recent years, the idea that their present location is the result of orbital migrations rather than their true formation location has progressively emerged. Specifically, some asteroids could be comets, and some comets could be TNOs. Here, I present the studies carried out along my PhD aiming to constrain the physical properties of all these populations in order ultimately i) to determine the link between these populations, ii) bring key constraints to their past orbital evolution and thus iii) key constraints to the formation and evolution models for our Solar System. For that purpose, I have used spectroscopy as a main tool, as well as data modelling using a radiative transfert code and comparison of our astronomical data to laboratory measurements of meteorites and cosmic dust.