CAREER: The True Mass-Radius-Period Distribution of Small Exoplanets

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One of the chief goals in exoplanet research today is to understand the mass distribution of planets in the universe. Having accurate masses will help establish mass/density vs. orbital radius relationships, and to identify rocky Earth-like planets in the habitable zone. These advances represent an important new avenue to understanding planetary formation processes. The work proposed here will mine the Kepler data and use new techniques to identify masses of planets in all 706 multi-transit (multi-planet) systems observed by the Kepler spacecraft. Right now, masses can be estimated for about 10% of this sample: the systems in which transit-time variations (TTVs) are observed. The results of this work will guide future observations and searches done for Earth-like planets, be they done with space-based telescopes, such as JWST, or ground-based telescopes, such as the future US-ELTs. Outreach and education efforts include the mentoring of at least five students from under-represented groups, the development of research-based education resources, the development of a library of animated gifs related to astronomy, and supporting development of a chapter on exoplanets in an OpenStax astronomy textbook.The team will conduct an analysis of all 706 Kepler multi-transiting systems (MTSs) using their publicly-available PhotoDynamical Multi-planet Model (PhoDyMM). A photodynamical model includes the full n-body dynamical evolution of a planetary system, but fits directly to the Kepler photometric lightcurve itself. Until now, most analyses of MTSs have relied upon transit timing variations (TTVs) as the multiple planets tug each other around, slightly delaying or accelerating expected transits. Full photodynamical analysis has been applied to only 20 of the 706 known Kepler MTSs. This technique also makes use of the Kepler short cadence data, which traditional TTV analysis typically ignores. In addition to finding masses for many super-Earths and other larger planets, the team expects to make at least 50 new mass determinations of the smallest exoplanets, until now inaccessible to current methods. This method has the promise to detect new planets at the lower end of the mass distribution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.