Brett Gladman

Over the past two decades, our knowledge of the Solar System’s transneptunian region (often called the Kuiper Belt) has been gradually increasing. Observational surveys have greatly expanded the inventory of Trans-Neptunian Objects (TNOs), which are distant icy bodies thought to be relics from the giant planet formation era.In the main Kuiper Belt region, a complex bimodal inclination structure is present, leading to the common assertion that current TNOs may have accreted in different regions of the protoplanetary disk. To study this blended inclination structure, I develop an improved semi-analytical method to compute TNO ‘free’ inclinations, which are well conserved and thus better represent the primordial inclination profile.In the implanted Kuiper Belt, a semimajor axis power law distribution is observed in the outer Solar System surveys. I show that in a patched-conic model, the power law is a natural outcome after multiple flybys of the perturbing planet homogenize the directions of planetary relative-velocity vectors. This model allows one to analytically compute the diffusion coefficient in closed form.In the distant Kuiper Belt, several striking features seem to challenge our previous understanding of the early Solar System: 1) a very large population of objects in distant mean-motion resonances with Neptune, 2) a substantial detached population that are not dynamically coupled with Neptune’s effects, and 3) the existence of three very-large perihelion objects. I demonstrated in this thesis, that a super-Earth-mass planet temporarily present in the Solar System on a Neptune crossing orbit (referred to as a ‘Rogue Planet’), is able to create all these structures in the distant Kuiper Belt. Such a planet would have formed in the giant planet region and gotten scattered to a highly-eccentric orbit with a few hundred au semimajor axis with a typical lifetime of 100 Myr. Additionally, I showed this transient planet would not have heated the cold belt’s very low free inclinations to larger than observed. Both the structures in the distant belt and the existence of an unheated cold belt provide constraints to narrow down the mass and possible dynamical histories the rogue might have taken.

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All four giant planets have satellites with large inclined eccentric orbits thatare known as irregular moons. This thesis contains the results of searches forirregular moons around two of the giant planets, Jupiter and Saturn. Bothsearches consisted of stacking multiple images to detect moons smaller thanhave been discovered before. From a square degree field, 52 jovian mooncandidates were found, of which seven were linked to known moons. Fromtwo separate 1.1 square degree fields, 120 saturnian candidates were found,with 40 of them linking to previous discoveries.Extrapolating the detections to the entire irregular moon populations ofboth gas giants, there are (to within a factor of 2) 600 jovian moons downto a diameter of 0.8 km, and 150 ± 30 saturnian moons down to a diameterof 2.8 km. Both sets of detections were used to create luminosity functionsof the two irregular moon populations. At the faintest magnitudes of bothluminosity functions, exponential indexes α were measured to be 0.29 ± 0.15and 0.78 +0.14 −0.12 , corresponding to a differential diameter power law of indexesq ~ 2.5 and ~ 5, respectively. These slopes imply that the jovian irregularmoon population is in collisional equilibrium and the saturnian populationhad a recent (0.1-2.8 Gyr) large collision.

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The Trans-Neptunian objects (TNOs) preserve evidence of planet building processes in their orbital and size distributions. While all populations show steep size distributions for large objects, recently a relative deficit of Neptunian Trojans and scattering objects with diameters D99% confidence. The fact that three independent samples of three different populations show this trend suggests that it is a real feature, possibly shared by all hot TNO populations as a remnant of ''born big'' planetesimal formation processes. We surmise the existence of 9000 ± 3000 Plutinos with absolute magnitude Hr ≤ 8.66 and estimate 37000 +12000/-10000 Plutinos with Hr ≤ 10.0 (95% confidence ranges). Our survey also discovered one temporary Uranian Trojan, one temporary Neptunian Trojan and one stable Neptunian Trojan.With these discoveries, combined with our survey characteristics, we derive populations of 110 +500/-100, 210 +900/-200 and 150 +600/-140 for these populations, respectively, with Hr ≤ 10.0.With such approximately equal numbers, the temporary Neptunian Trojans cannot be previously stable Trojans that happen to be escaping the resonance now; they must be captured from another reservoir. Our population estimate also reveals that the Neptunian Trojans are less numerous than the main belt asteroids (semi-major axis 2.06
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Studying the orbital dynamics of small body populations in the Solar System allows us to understand both their current population and past orbital structure. Planet-crossing populations can also provide impact speeds and probabilities, and when coupled to cratering histories of solid bodies can provide planetary surface ages.The Wide-field Infrared Survey Explorer Near-Earth Object (NEOWISE) detections of the near-Earth object (NEO) orbital distributions (Mainzer et al. 2012) are used to illustrate that a pure-gravity NEO orbital model (Greenstreet et al. 2012) is not rejectable (at >99% confidence). Thus, no non-gravitational physics is required to model the NEO orbital distribution.We discovered in the NEO model numerical integrations the unexpected production of retrograde orbits from main asteroid belt sources, estimating that ~0.1% of the steady-state NEO population is on retrograde orbits. These retrograde near-Earth asteroids (NEAs) may answer two outstanding questions in the literature: the origin of two known MPC NEOs with asteroidal designations on retrograde orbits and the origin of high-strength, high-velocity meteoroids on retrograde orbits.Moving to the outer Solar System, we constructed a Centaur (a_Jupiter
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The small body populations within a planetary system give information about the planet formation and migration history of the system. In our Solar System, we study these bodies (asteroids, comets, and trans-Neptunian objects), by directly observing them in reflected light. In other solar systems, dust traces the position of the planetesimal belts that produce it, and is observed as an excess above the stellar flux in the infrared. The dust is visible and not the planetesimals because of the much greater cross-sectional surface area of a swarm of dust particles. In this thesis, both leftover large planetesimals in our Solar System and dust around other stars are investigated.Data from the Canada-France Ecliptic Plane Survey (CFEPS) are used to measure the absolute populations of trans Neptunian objects (TNOs) in mean-motion resonances with Neptune, as well as constrain the internal orbital element distributions. Detection biases play a critical role because phase relationships with Neptune make object discovery more likely at certain longitudes. The plutinos (objects in the 3:2 resonance) are given particular attention because the presence of the secular Kozai resonance within the mean-motion resonance causes different detection biases that need to be accounted for to properly debias surveys that include detections of plutinos. Because the TNOs that are trapped in mean-motion resonances with Neptune were likely emplaced there during planet migration late in the giant planet formation process, the structure within and relative populations of the resonances should be a diagnostic of the timescale and method of giant planet migration. Exoplanet systems that host several rocky planets are those that did not experience giant planet migration, and thus are likely to host planetesimal belts which should be detectable as debris disks. The Kepler Mission has detected a host of such systems, and we use data from the Wide-field Infrared Survey Explorer (WISE) Mission to search for debris disks around these stars. Though we tentatively detect more excesses toward these stars than would be expected, contamination from warm dust in the Milky Way Galaxy makes detection unreliable for these systems, and will have to await future infrared space telescopes.

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