UC Riverside

Exoplanet discoveries have proved numerous planetary system orbital configurations, including the discovery of exoplanets on highly elliptical orbits. The most eccentric planet in our own solar system, Mercury, exhibits an eccentricity of only 0.205, and Earth’s eccentricity is a mere 0.017. By comparison, exoplanets have been discovered with orbital eccentricities ranging from zero to 0.956 (HD20782, Kane et al. 2016). Because the eccentricity of a planet is largely responsible for its received stellar insolation, and thus its climate and habitability, it is crucial to be able to model this value in the absence of measurements. The prevailing theory explaining the enhanced ellipticity observed is that dynamical instabilities can cause eccentric orbits by planet-planet scattering where one planet is ejected from the system and, in accordance with the law of conservation of angular momentum, the other is left to undertake an eccentric orbit. Furthermore, it has been observed that low-mass stars are less likely to harbor giant planets than massive stars (Nielsen et al. 2019). Thus, the higher frequency of giant planets around more massive stars may lead to interactions whose signatures remain in the angular momentum of eccentric orbits. This work aims to connect eccentricity distributions to planet formation and dynamical evolution models by investigating possible correlations of eccentricity with host star mass and chemical composition. We describe series of statistical data analysis techniques, including to identify patterns in the distribution of exoplanet eccentricities and correlations with host star properties. Such correlations may have significant implications for the relative occurrence rate of terrestrial planets in systems where giant planets are more likely to exclude their orbital integrity.