Wide binaries as a critical test for Gravity theories

TL;DR

This paper proposes using wide binary star systems as a critical test for modified gravity theories, finding evidence that supports deviations from Newtonian predictions at low accelerations similar to galactic rotation curves.

Contribution

It introduces a novel test using wide binaries to distinguish between dark matter and modified gravity, providing observational evidence consistent with modified gravity predictions.

Findings

Relative velocities are constant across wide binary separations.

Results suggest a breakdown of Kepler's third law at low accelerations.

Data aligns with predictions of modified gravity theories.

Abstract

Assuming Newton's gravity and GR to be valid at all scales leads to the dark matter hypothesis as a requirement demanded by the observed dynamics and measured baryonic content at galactic and extragalactic scales. Alternatively, modified gravity scenarios where a change of regime appears at acceleration scales $a<a_{0}$ have been proposed. This modified regime at $a<a_{0}$ will generically be characterised by equilibrium velocities which become independent of distance. Here we identify a critical test in this debate and we propose its application to samples of wide binary stars. Since for $1 M_{\odot}$ systems the acceleration drops below $a_{0}$ at scales of around 7000 AU, a statistical survey of wide binaries with relative velocities and separations reaching $10^{4}$ AU and beyond should prove useful to the above debate. We apply the proposed test to the best currently available data. Results show a constant upper limit to the relative velocities in wide binaries which is independent of separation for over three orders of magnitude, in analogy with galactic flat rotation curves in the same $a<a_{0}$ acceleration regime. Our results are suggestive of a breakdown of Kepler's third law beyond $a \approx a_{0}$ scales, in accordance with generic predictions of modified gravity theories designed not to require any dark matter at galactic scales and beyond.