Description:

Thanks to GAIA, ultra-wide stellar binaries have recently reasserted themselves as key probes of the Galactic environment, of dark matter substructure, and even of our understanding of gravity itself. Wide binaries are also a theorist's dream: a system which in isolation is exactly solvable, and whose dynamical evolution due to (i) stochastic kicks from passing stars, molecular clouds, etc., and (ii) and secular torques from the Gallactic tide, can be predicted beautifully with perturbation theory. In this talk I will first describe some of the curious observations that have arisen around wide binaries in the last few years. I'll then focus on the highly unusual 'superthermal' distribution of wide binary eccectricities. Using Hamiltonian dynamics and kinetic theory, I will prove that neither effect (i) or (ii) can be responsible for producing this superthermal distribution, and explain what this tells us about wide binary formation mechanisms. I will conclude with some predictions that can be tested with future GAIA data releases.

Chris Hamilton, Postdoctoral Fellow, Institute of Advanced Study, Princeton

Host: Lena Murchikova