APF-50: A robotic search for Earth's nearest neighbors

2017 • 2017PhDT.......136F

Authors • Fulton, Benjamin J.

Abstract • The discovery of thousands of exoplanets during the past decade opened the door to detailed studies of exoplanet demographics. Now we are able to group planets into different categories based on observable characteristics and study population-level properties. Patterns and trends in the known population of planets are emerging which provide insight into the processes that drive the formation and evolution of exoplanets. In this work we develop the tools necessary to discover and accurately characterize a statistically useful sample of exoplanets. We use these tools to discover several new planets and examine the mass function of small planets orbiting bright, nearby stars. By leveraging the fully-robotic Automated Planet Finder telescope, we conduct the ''APF-50'' Doppler survey which provides greater sensitivity to low-mass planets than was previously possible with classically-scheduled instruments. We study the planet population orbiting stars similar to our sun and also the ultimate fate of these planetary systems by searching for planets orbiting white dwarfs. To date, the statistical power of NASA's Kepler mission remains unmatched due to the shear number of planet detections and unprecedented sensitivity to small planets. We utilize the Kepler dataset combined with high-resolution spectroscopy from Keck Observatory to re-examine the radius function of small planets in fine detail. We find that planets between the size of Earth and Neptune typically fall into one of two distinct size groups. We discuss the implications of these findings by comparing to the mass function of small planets measured by the APF-50 survey and find that we are only just beginning to scratch the surface of the population of small planets that Kepler found to be so prevalent. This discovery supports the emerging picture that close-in planets smaller than Neptune are composed of rocky cores measuring 1.5 R ⊕ or smaller with varying amounts of low-density gas that determines their total sizes.

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