The eccentricity distribution of wide binaries in the Galaxy

GAIA has allowed astronomers to probe for the first time the phase space distribution function (DF) of the Keplerian orbital elements of wide binaries in the Solar neighbourhood. This DF exhibits non-trivial features, in particular an unexplained superthermal distribution of eccentricities for binaries with semimajor axes >1000 AU. To interpret such features we must first understand how the binary DF is affected by dynamical perturbations, which typically fall into two classes: (i) stochastic kicks from passing stars, molecular clouds, etc. and (ii) secular torques from the Galactic disk. In this talk I will isolate effect (ii) and show how one can compute the time-asymptotic, phase-mixed DF for an ensemble of wide binaries under the Galactic tide. I will discuss what the resulting eccentricity and inclination distributions can tell us about the formation mechanisms of wide binaries in the Milky Way.