Expansion-induced contribution to the precession of binary orbits

TL;DR

This paper investigates how the expansion of the universe can influence local binary systems, revealing effects on orbital precession and eccentricity beyond standard general relativity predictions.

Contribution

It introduces a model using McVittie spacetime to quantify how cosmic expansion affects binary orbit precession and eccentricity, highlighting effects not previously considered.

Findings

Expansion affects orbital precession beyond GR predictions

Eccentricity of orbits can change due to expansion

Numerical estimates demonstrate measurable effects

Abstract

We point out the existence of new effects of global spacetime expansion on local binary systems. In addition to a possible change of orbital size, there is a contribution to the precession of elliptic orbits, to be added to the well-known general relativistic effect in static spacetimes, and the eccentricity can change. Our model calculations are done using geodesics in a McVittie metric, representing a localized system in an asymptotically Robertson-Walker spacetime; we give a few numerical estimates for that case, and indicate ways in which the model should be improved.