Honors College

Document Type

Honors Thesis




Neil Comins

Committee Members

David Batuski, David Clark, Saima Farooq, Ronald Nadeau

Graduation Year

May 2020

Publication Date

Spring 5-2020


This project investigates the stability of observed planetary systems, and whether this stability remains in the presence of additional outer planets. This made use of the program Mercury6, an n-body integrator that computes the changes in planetary orbits over time. The Systems HD 136352, GJ 9827, and HD 7924 were studied with initial conditions taken from the available observational data. This information was curated using the online NASA Exoplanet archive of confirmed exoplanets. With these initial conditions, Mercury6 computed the changing planetary orbits of each system for 5 million years. For each of these systems, a single outer planet, which was varied in mass and semi-major axis, was added to test the effect on the resultant data. Three distinct cases emerged. For GJ 9827, a system with very low semi-major axes and initial inclinations, complex oscillatory behavior in the inclination of the planets emerged, with variations based on mass and orbital distance of the additional outer planet. For HD 136352, complex oscillatory behavior was observed in the planet eccentricities. For HD 7924, instability occurred in the first 250 thousand years for the observed system. Tested with perturbing bodies, HD 7924 was shown to have stability in a number of cases, which could be evidence that additional unseen planets are present within the system. A potential conclusion from this data is that long-term repetitive oscillations can be indicative of stability, and that computational methods similar to the use of Mercury6 have significant potential in the field of planetary science.