Professor Eric Agol from the University of Washington will be the featured speaker at an upcoming Department of Physics and Astronomy colloquium. His talk is titled, "An Assay of the TRAPPIST-1 System."
The two most prolific techniques for detecting exoplanets are complementary: radial velocities yield planet masses, while transits yield their radii. Yet, to measure the density of a planet we need both quantities, from which we can "assay" the composition. However, these two techniques have only been applied to a single rocky, temperate planet (LHS 1140b, which is about six times as massive and 40% larger in radius compared with Earth).
Agol will introduce the TRAPPIST-1 system for which we can measure the masses *and* radii of *seven* temperate, *Earth-sized* exoplanets for the first time. The technique used is transit-timing variations caused by gravitational interactions of the planets, developed together with UNLV professor Jason Steffen.
He will describe the barriers to the applying this technique: degeneracies in the modeling, stellar variability, and high dimensionality. We are addressing these with new data from the Spitzer Space Telescope to measure "chopping", and with modern data analysis tools, including Gaussian Processes, Differentiable Programming, and Hamiltonian Monte Carlo.
Agol will conclude with the future prospects for studying this planet system with the James Webb Telescope and full photodynamical modeling.