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Title: The effect of wide-orbit planets on inner planetary systems and debris
Author: Read, Matthew James
ISNI:       0000 0004 7230 7722
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2018
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Planetary systems around other stars have been observed to be far more diverse than what would be expected from the example of the Solar System. Exoplanets have been detected with a wide range of sizes and separations from the host star, with a range of orbital properties including large eccentricities and small inter-planet mutual inclinations. How representative these planetary systems are, however, is unclear due to detection techniques being more sensitive to planets on close orbits around the host star. It is possible therefore that a population of wide-orbit planets could be present in these systems and be evading detection. These planets may play a significant role in forming and shaping planetary systems, resulting in the architecture that is observed today. Currently, one of the major ways of inferring the presence of wide-orbit planets, besides directly detecting them, is to consider the dynamical impact they would have on known planets. In the first part of this thesis I consider how the eccentricities of known planets are affected due to long term dynamical interactions with a wide-orbit planet. I show that the eccentricity of a known planet in a system can periodically be significantly increased due to these interactions, provided that there are a total of two planets in the system. For systems with multiple known planets I show that the inner planets can protect each other against long term eccentricity perturbations from a wide-orbit planet. Following on from this investigation, I show how the inclinations of planets are affected due to long term interactions with a wide-orbit planet. Specifically, I consider how this interaction affects the probability that planetary systems are observed to transit. I find that the presence of wide-orbit planets in transiting planetary systems can help explain the so-called `Kepler-Dichotomy' which describes the apparent excess of observed single transiting systems compared with multi-planet transiting systems. Wide-orbit planets do not just dynamically interact with other planets in a system but also with small debris type bodies, akin to the Asteroid and Kuiper belts in the Solar System. In the second half of this thesis, I consider the planetary system HR8799 which is known to host four planets and two populations of debris which lie both internally and externally to the known planets. I find, through suites of N-body simulations, that a hypothetical planet in HR8799 sculpts an outer debris population that agrees more strongly with observations, compared with what would be expected by considering the known planets in isolation. Finally, for the last part of this thesis, I describe a survey that is looking to observe wide-orbit planets in close-by planetary systems directly. The observations and analysis for this survey is currently on-going, however I show preliminary results including systems with and without potential companion detections.
Supervisor: Wyatt, Mark ; Kennedy, Grant Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Planets ; Dynamics ; Debris ; Observations