UCLA

The purpose of this thesis is to further describe the effects of secular resonances between planets at low inclinations and eccentricities with a special focus on the interactions between these resonances and stellar oblateness. To accomplish this, I led four projects. The first project evaluated the stabilizing power of general relativity precession against external perturbation on compact multi-planet systems. I extended existing stability criteria that neglected general relativity, evaluated the proportion of the exoplanet sample for which the updated criteria produces qualitatively different conclusions, and investigated the stability of undetected inner planets within coplanar observed multi-planet systems. My second project further explored the stability of undetected inner planets within observed systems by considering the effect of evolving stellar oblateness on potential secular resonances. I find that, consistent with previous theory, evolving stellar oblateness causes secular resonances between planets to move through parameter space, causing a wide range of potential inner planet orbits to experience resonance. These sweeping resonances systematically transfer angular momentum between planets, permanently changing the mutual inclinations between planets.In my third project, I consider the three-planet transiting exoplanet sample at large and investigate how often these sweeping resonances from evolving stellar oblateness occur. Ignoring stellar oblateness, these resonances should be exceptionally rare, requiring almost fine-tuned selections of planetary semimajor axes and masses. However, I demonstrate that the resonance-sweeping vastly increases the regions of parameter space where these resonances may occur. Investigating a clean sample of thirty three-planet systems, I find six (20% of the sample) that have masses and semimajor axes that are susceptible to these resonances if their host stars were born with sufficiently high spins. I argue that this finding of 20%, even if only from a sample of thirty, indicates that such resonances are commonplace among the histories of planetary systems. In my fourth project, I show that sweeping resonances from evolving stellar oblateness resonances have significant impact on the observational outcomes of multi-planet transiting systems as they greatly modify the mutual inclinations between planets. As the outer two planets of three planet systems typically align as a result of these resonances, the probability they are observed transiting together increases. However, the inner planet is misaligned from them as a result, reducing the overall probability that the system is observed as a two- or three-planet transiting system. I discuss the implications these systematic effects on transit probabilities may have on the observed exoplanet sample.This thesis demonstrates that events early in the life of a planetary system, such as the stellar spin-down, have long-lasting effects on systems’ architectures, and provides insight into how these early events can systematically shape what planetary systems are most amenable to observation.