Special Physics Seminar

Choose Your Own Adventure: Planets among the Smallest Stars

Sarah Ballard

University of Washington

The Solar System furnishes the most familiar planetary architecture: many planets, orbiting nearly coplanar to one another. However, the most common planetary systems in the Milky Way orbit much smaller M dwarf stars, and these may present a very different blueprint. The Kepler data set has furnished more than 100 exoplanets orbiting stars half the mass of the sun and smaller. Half of these planets reside in systems with at least one additional planet. I investigate the proposition of self-similarity in this sample: whether a single architecture explains the multi-planet yield of Kepler. In fact, the data much prefer a model with two distinct modes of planet formation around M dwarfs, which occur in roughly equal measure. One mode is one very similar to the Solar System in terms of multiplicity and coplanarity, and the other is very dissimilar. I discuss whether stellar properties are predictive of one final architecture over the other, and describe implications in the search for life. Ultimately, the deluge of forthcoming exoplanet discoveries will require cheap observables to prioritize precious followup resources, and I'll describe how to leverage planet multiplicity to maximize science return.