Gas Giants in Extreme Environments

In this thesis, I will explore three ideas that relate to giant planet formation, an incredibly dynamic process that affects not only the orbital configurations, but also the atmospheric structure and processes driven by the often extreme environments in which these planets are embedded:(1) The formation of our solar system's ice giants may have involved significant migration due to a disk dynamical instability, as well as concurrent accretion of solids and gas from the protoplanetary disk, that may have consequences for their current atmospheric composition and evolution. (2) In exoplanetary systems, gas giants have been discovered on orbits that are extremely eccentric, and in the inner regions corresponding to the traditionally rocky planet region of our own solar system. These exotic systems may have undergone a phase of giant impacts, analogous to the phase that shaped our solar system's inner planet region and resulted in the Moon-forming impact. Such a phase produces outcomes that reproduce interesting features of the population: the correlation of mass with eccentricity, and eccentricity with stellar metallicity. (3) Finally, the atmospheres of the close-in planets are bathed in stellar irradiation. Photochemical reactions occur as the upper layers of the atmospheres are irradiated, and the massive amounts of deposited energy drive hydrodynamic winds from the planets. This results in mass loss that can not only be observed in the cases of giants, but can shape the global structure of smaller planets, leaving an imprint on entire populations of these planets