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Orbital outcomes of STIPs and consequences for hot-Jupiter formation and planet diversity Granados Contreras, Águeda Paula


The discovery of exoplanets on short orbital periods (P < 100 days), including hot-Jupiters and Systems with Tightly-packed Inner Planets (STIPs), defies predictions from classic planet formation theory. Their existence requires either large-scale migration of planets through disks or rethinking fundamental steps in the planet formation process or some combination of both. It is further unclear whether the known STIPs harbor additional, undetected planets at even larger stellarcentric distances, which would have fundamental implications for how the systems formed. Through numerical simulations, we explore: (1) the in-situ formation of hot-Jupiters as an extreme outcome of early metastability of STIPs in the presence of gas; and (2) the dynamical effects of distant gas giants on STIPs using two case studies. In addition, we use synthetic systems to explore whether hot-Jupiters could form in-situ within dynamically unstable STIPs through the consolidation of a critical core M > 10 Earth-masses. We compare the dynamical outcomes of gas-free and gas-embedded planetary systems, in which consolidation of a critical core was only possible in the gas-free simulations. In contrast, STIPs are resistant to instability when gas is present, resulting in coplanar and nearly circular systems. The instability of the configurations after 10 Myr increases if the eccentricity is perturbed to e~0.01. In some cases, the planet-disk interaction produces co-orbiting planets that are stable even when the gas is removed. We explore the transit detectability of these configurations and find that the coorbital transit signature is difficult to identify in current transit detection pipelines due to the system dynamics. To explore STIP evolution in the presence of an outer giant planet, we vary the semi-major axis of the perturber between 1 and 5.2 au. We find that the presence of the outer perturber, in most locations, only alters the STIP precession frequencies but not its evolution or stability. In those locations where the perturber causes secular eccentricity resonances, the STIP becomes unstable. Secular inclination resonances can affect the observed multiplicity of transiting planets by driving the orbits of one or more planets to inclinations about 16 degrees.

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