Astronomy Colloquium: Building a Predictive Theory of Planet Formation: Extrapolation versus Phenomenology in the Era of Direct Imaging
Planetary bodies provide suitable environments for the emergence of life. Thus knowing their distribution as a function of mass, orbital radius, and bulk composition can help constrain the possible number of habitable worlds. Observations in the accessible regions of our Galaxy provide empirical constraints on planet populations. Yet extrapolation of these results to the rest of the observable Universe requires understanding the dependence of formation and evolution on a wide range of initial conditions. On the one hand, this process is simple: small bodies grow into larger ones through collisions (and sticking) of solid particles, or through local gravitational instabilities. On the other hand, the specific outcomes depend on a large number of complex processes requiring coupled understanding of dynamics, chemistry, and radiative transfer over several orders of magnitude in solid particle size, gas density and orbital radius. I will first introduce some simple theories of planet formation, and explore expected outcomes as a function stellar mass. Then I will summarize recent observations that constrain these theories with a focus on the power of direct imaging for “model-breaking”. Finally, I will discuss experiments (some underway with new IR instrumentation on 8-meter class telescopes, and others planned for future facilities) that aim to efficiently improve our understanding. While much near-term progress will be made studying gas giant planets through resolved imaging and spectroscopy, the direct detection of rocky planets around the very nearest stars should be possible with the next generation of extremely large telescopes.
If you would like to meet with the speaker, please contact the host, Prof. Ted Bergin.