In Situ Formation of Short Period Terrestrial Planets

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A team of scientists at the University of Washington will perform computer simulations of the formation of rocky planets around other stars. The idea that rocky planets in our own Solar System were formed from much smaller bodies explains many features of the Solar System. They will investigate whether this same idea can successfully explain the formation of the planetary systems found around other stars. Their results will address whether our own Solar System is an outlier in how it formed. The study will focus on the systems of planets very close to low mass stars, which are the most common of type of planetary system discovered. This program will allow university students to gain experience in high performance computing and the handling of “big data”. Some of the work will be done in small projects for undergraduate students participating in the University of Washington's Pre-Major in Astronomy Program (PreMAP). PreMAP provides under-represented students in STEM with research opportunities in astronomy.To date, planetary Systems with Tightly-packed Inner Planets (STIPs) are the most statistically well-represented type of exoplanetary system, making them an excellent testbed for planet formation theories. However, planet formation models designed to reproduce the structure of our own Solar System typically fail to explain the seemingly exotic population of STIPs. A key component of the standard model of terrestrial planet formation is the growth from approximately kilometer size bodies to full sized planets, a regime where the physics is dominated by gravitational interactions and collisions between bodies. The team will use a recently enhanced, highly scalable particle code to follow the evolution of planetesimals on short period orbits as they interact gravitationally and collide. The results from these simulations will then be passed to a symplectic particle code to follow the late stages of planet formation for many millions of dynamical times. Using planetesimal compositions motivated by protoplanetary disk chemistry models, compositions of the terrestrial planets that result will be predicted, allowing future observations observations of the atmospheric composition of STIPs with James Webb Space Telescope to validate or falsify the possibility of in situ formation. Additionally, the gravitational influence of an outer giant companion during the accretion process will be considered, which may provide ways to infer the presence of an undetected giant companion from the orbital and compositional properties of the terrestrial planetsThis 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.