Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Astronomy

Supervisor

Wiegert, Paul

Abstract

The search for planets around stars other than our Sun, known as "exoplanets", has made use of a variety of different methods. Some methods look for the planet itself through direct imaging. Other techniques search for the signature of planets in the light from its parent star. Such indicators of a planet include the dimming of the star as the planet passes in front of it (the Transit method) or the discrepancy in events that occur from the influence of unseen planets (the Transit Timing Variation method). These techniques allow the discovery of worlds not otherwise visible to telescopes, through the orbital dynamics of known worlds. This work pursues the premise of detecting hidden celestial bodies through their effect upon visible ones.

In the first chapter, I examine the usefulness of the Canadian space telescope, the Near Earth Object Surveillance Satellite (NEOSSat), as a tool for exoplanetary science. I performe follow-up observations of several targets from the Transiting Exoplanet Survey Satellite (TESS). These observations improve the orbital ephemerides and baselines for these ex- oplanets, as well as demonstrate the capabilities of NEOSSat as a tool for exoplanetary science.

In the second chapter, I examine whether moons around exoplanets ("exomoons") could be detected via the transit timing variations they exert upon their planet. Exomoons are exceptionally difficult to detect via transits, but an exomoon could reveal itself through the gravitational effect it has upon on its parent planet. Thirteen Kepler systems are explored to determine whether this hypothesis could hold. The observed behaviour of eight systems is consistent with the presence of an exomoon, though this is insufficient to confirm the existence of a moon.

In the third chapter, I examine the debris disk around HD 181327. It shows a significant asymmetry in its surface brightness profile when viewed in visible light. By performing N-body simulations, I find that a 2-5 Jupiter-mass planet on a circular orbit at 62 au could produce and maintain a similar feature to that observed. Gravity is the universal architect of planetary systems.

The existence of a hidden celestial body can be betrayed by its gravitational influence upon another. In this thesis, I explore new ways of using gravity in this vein.

Summary for Lay Audience

Gravity is a ubiquitous force that connects all matter throughout the universe. While planets primarily orbit their host star, their true paths through space are determined by everything in the system. Every body tugs on every other, creating a complex and constantly changing web of gravitational connections. When one examines the resultant path through space closely, the motion is more complex than a simple elliptical path. This understanding has been used in our own solar system. In the 19th century astronomers observed the planet Uranus moving in an unexpected way, suggesting that something unseen must be altering its motion through space. The prediction of another planet pulling on Uranus led directly to the search for and discovery of Neptune.

The study of planets outside of our own solar system ("extra-solar planets" or "exoplanets") can also make use of gravitational interactions. Exoplanets are inherently very difficult to see directly because of their distance and faintness, and any light we might receive from a planet is often overpowered by the brightness of the star. Yet, we can still find exoplanets through other methods. Thousands of other worlds have been discovered, many of which by watching how the planets affect the motion of their parent star or another planet.

This research explores some new ways of using gravitational interactions to detect other bodies in exoplanet system. In the first paper, new observations of exoplanets with a Canadian space telescope are made to confirm the existence of these bodies. In the second paper, known observations of various planetary systems are examined and reverse engineered to predict potential extra-solar moons ("exomoons"). In the third paper, the uneven behaviour of dust grains in a young planetary system is analyzed to predict the existence of a new planet.

Planetary systems are sculpted through gravity, the nature of gravity allows us to deconstruct these planetary systems and then find new bodies that we cannot see directly.

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