Constraining the Flatness of Planetary Systems

Over the past 30 years, nearly 6,000 exoplanets have been discovered, revealing a remarkable diversity of planetary systems. Essential information about the formation of these systems can be found in their current architectures, as they serve as a signature of their dynamical evolution. Much of what we currently know about architectures comes from the study of stellar obliquities--the angle between the stellar spin axis and the planet's orbital normal--in hot Jupiter systems. However, hot Jupiters are intrinsically rare, with an occurrence rate of 1%, highlighting the need to explore architectures in a broader range of planetary systems. In this thesis, I study the architectures of planetary systems beyond hot Jupiters, focusing on warm Jupiter and Neptune systems through stellar obliquity measurements. Using VLT/ESPRESSO observations of the Rossiter-McLaughlin effect, I have found that these different exoplanet populations have different obliquity distributions: i) hot Jupiters show a two-component distribution, with one population of aligned systems and another approximately isotropic population of misaligned systems; ii) independent of their eccentricities, warm Jupiters are typically well aligned; iii) Neptunes appear to have a bimodal distribution of well-aligned and polar systems. These contrasting obliquity distributions suggest distinct formation pathways for each population. Finally, I also discuss prospects and make predictions for measuring mutual inclinations--the angle between different orbital planes of different planets in the same system--using future Gaia astrometric data. I show that these measurements have the potential to provide deeper insights into the formation and evolution of a larger and more diverse sample of planetary systems.