"IT TAKES TWO:
ON THE SECULAR AND STOCHASTIC DYNAMICS
OF THE WEIRD WIDE BINARIES IN THE MILKY WAY"

Abstract: ABSTRACT
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) secular torques from the Galactic 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
eccentricities. 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.
Based upon Hwang et al. (2022); Hamilton (2022); Modak & Hamilton (2023); Xu et al. (2023).