Unraveling Exoplanet Formation and Evolution with Precise Relative Kinematic Ages

Tidal interactions between short-period planets and their host stars circularize eccentric orbits, realign angular momenta, alter rotation periods, and remove energy from a planet’s orbit. Theoretical predictions about the efficiency of these tidal processes are highly uncertain, and stellar age uncertainties further complicate exoplanet system formation and evolution inferences. Using the Galactic velocity dispersion as a proxy for the relative ages of exoplanet host star populations, I have established that hot Jupiters inspiral due to tides before their host stars end the main sequence phase of their evolution. While a similar fate was expected for ultra-short-period or USP planets (i.e., rocky planets with orbital periods less than one day), I demonstrated that USP planets are robust to tidal decay. My observation requires that due to their shorter periods and/or lower masses, USP planets trigger less efficient tidal dissipation within their host stars than hot Jupiters. Using a similar approach, I have found that misaligned hot Jupiter systems are relatively older than aligned hot Jupiter systems. I argue that the best explanation for this observation is that misaligned hot Jupiters arrive at their orbits after the dissipation of their parent protoplanetary disks. I showed that Kepler multiple-planet systems with near-resonant planets are younger than systems far from resonance, even for systems where tidal dissipation cannot be responsible for moving planet pairs away from commensurability. This observation implies that non-tidal secular processes drive systems away from resonances.