CAREER: Planet Formations in the Age of Kepler

In the past few years, NASA’s Kepler space telescope has discovered thousands of extrasolar planet candidates. Many more discoveries are almost certain to come in the next few years. This is an unprecedented windfall for scientists who wish to understand how planets form, and how they ultimately arrive at their majestic orbital configurations. The PI, Dr. Lithwick, plans to capitalize on Kepler’s results by developing understanding of planet formation and educating the public about recent advances. Intellectual merit • Dr. Lithwick will tease out the dynamical history of the Kepler planets by examining their current orbital characteristics. His recent work shows that Kepler systems experienced prolonged dissipation in the past. He plans to use observed transit-time-variation (TTV) signatures to measure masses and orbits, employing his newly derived simple analytical expressions. He will also extend his expressions to treat other effects, such as three body resonances and higher-order terms, and thereby learn as much as possible about the Kepler planets’ properties. He then plans to reverse engineer these systems by simulating environments that could have led to their current observed states. • The PI will also approach the problem from the other direction—from first principles—by developing the theory for how planets form out of planetesimals. An important ingredient is often neglected in theories of planet formation: the role of rapid collisions amongst the swarm of small bodies from which planets emerge. These collisional small bodies are crucial for defining the final planetary systems, including the masses of solid planets, the timescale for their formation, and their emergent orbital configurations. They dynamically cool the planets’ orbits, and hence are a leading candidate for the prolonged dissipation experienced by the Kepler systems. The PI will extend his previous studies by running simulations that include many collisional small bodies, and will simultaneously build a theory to explain the results. He will apply these results to explain the formation of not only the Kepler planets, but of other systems as well, including the terrestrial planets, the Kuiper belt, and the moons of Uranus and Pluto. Broader Impacts The PI plans to integrate these research activities with the following educational ones. • Dr. Lithwick will work with around 12 high school teachers to (a) guide them in developing curricular materials on the topic of extrasolar planets; and (b) help them guide some of their students in carrying out longer-term independent research projects on planetary systems. Both activities will emphasize computer simulations in order to develop the students’ computational thinking skills. • He will increase the number of talks to the public he has been giving on these topics at the Adler planetarium, and will have the postdoc and graduate student funded by this grant give talks at the Adler.