Aaron M. Geller

Dynamical Evolution of Planetary Systems in Star Clusters
Contact information:
Northwestern University
CIERA / Department of Physics & Astronomy
2145 Sheridan Road
Evanston, IL 60208-3112
Fellowship status:
Starting year: 2013
Research Interests:

Today, detailed observations are revealing a rich panoply of exoplanets in our Galaxy. Many are multi-planet systems. Some show surprisingly different characteristics from our own Solar System that pose serious problems for standard isolated planet formation theories. Strong evidence indicates that the majority of stars form in clusters, many of which dissolve within a Hubble time. Therefore many of the exoplanets we observe today (in both clusters and the field) may have been born inside star clusters, and subjected to past perturbations from nearby stars. Understanding how stellar encounters within this birth environment affect the dynamical evolution of planetary systems is paramount to interpreting the characteristics of exoplanets discovered by Kepler, CoRoT, OGLE, HAT, WASP, JWST, ground-based RV surveys, etc., and how these relate to the planet formation epoch. To address these important questions, the PI proposes to continue working with a team of experts to complete development an N-body code to self-consistently simulate the dynamical evolution of multi-planet systems in realistic star clusters. The PI will use this code to model the nine open clusters, including four in the Kepler field, that have been surveyed comprehensively for transiting exoplanets. Each cluster will be modeled with multiple different initial planet populations to cover the range in characteristics of observed exoplanets. The simulations will be analyzed, accounting for the unique sensitivity limits of each transit survey, and the results will be compared directly with the observations. This project will reveal, for the first time self-consistently, how stellar encounters within star clusters of a wide range in age, density, mass, etc. influence the dynamical evolution of multi-planet systems (including those like our Solar System), and how the characteristics of exoplanets we observe today in both clusters and the field may have been modified in the past by their birth environment.

Education and Outreach Interests:

Despite the significant increase in access to computers and other technology within our Nation’s high schools, quality curricula for teaching high-level computing skills and computational thinking have not developed at the same pace. This lack of necessary curricula is most pronounced in schools within lower socioeconomic areas, and is also shown to discourage women and minorities from pursuing careers in the sciences. The PI proposes to help address this problem by working with Dr. Kalogera and the Northwestern (NU) GK-12 and CE21 programs (both funded by the NSF) to develop, test and disseminate about 15 high school lesson plans based on the scientific research in this proposal. The PI will work directly with NU GK-12 graduate students to develop about 5 classroom-tested high school lesson plans per year. To supplement the lesson plans, the PI will also develop a web-based student-friendly interface to both analyze the products of the proposed simulations and to allow students to run simulations of their own. During years 2 and 3 the PI will work with Dr. Kalogera and the CE21 team to integrate these lesson plans into teacher professional development workshops, which the PI will co-lead. Through these workshops, the PI will train about 20 Chicago Public School and area teachers to use his lesson plans, thereby reaching roughly 2000 students with his curricular materials by the end of the fellowship.