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Utilizing Kepler and K2 to Advance Exoplanet Demographics

  • Author(s): Zink, Jonathon Kenneth
  • Advisor(s): Hansen, Bradley M. S.
  • et al.
Abstract

To understand the uniqueness of our solar system, we must assess the system architectures and demographic features existing in the known planet population, but such a task requires a homogeneous set of candidates. Fortunately, the Kepler spacecraft continuously collected photometry from a single patch of the sky, which in turn produced a well characterized catalog of transiting exoplanets. However, previous studies assumed multi-planet systems were subject to the same selection effects as their single-planet counterparts. I investigate this assumption, finding that a proper completeness accounting significantly increases the underlying occurrence of multi-planet systems to 5.86 planets per FGK dwarf and only requires a 1.5 degree average system mutual inclination. Using this correction I provide an updated extrapolation of the occurrence of Earth analogs and find that 5.9% of GK dwarfs have more than one planet within their habitable zone.

Additionally, the K2 mission collected photometry from 18 fields along the ecliptic plane, providing a unique opportunity to understand how exoplanet formation may be affected by galactic latitude, stellar metallicity, and stellar age. For my thesis, I developed a fully automated pipeline able to detect and vet transit signals in K2 photometry, enabling assessment of sample completeness and reliability. This catalog contains 768 planets, with 235 newly identified candidates. Correspondingly, I present the first uniform analysis of small transiting exoplanet occurrence outside of the Kepler field, finding a metallicity dependence in small planet occurrence.

I also discuss how the Sun’s late stage evolution and the existing solar system architecture will capture Jupiter and Saturn into a mean-motion resonance. Eventually perturbations from passing stars will trigger large-scale instability, culminating in the disassociation of all outer planets. Extrapolating this result to other systems indicates a temporal dependence on bound planet occurrence in the Galaxy.

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