Published April 2026 | Version Published
Journal Article Open

A Quality Framework for Testing Gravity with Wide Binaries: No Evidence for MOND

  • 1. Independent Researcher, Crawley, UK
  • 2. ROR icon University of Portsmouth
  • 3. ROR icon California Institute of Technology
  • 4. ROR icon Queen Mary University of London
  • 5. ROR icon Leiden University
  • 6. ROR icon University of Cambridge

Abstract

Wide binaries (WBs) offer a unique opportunity to test gravity in the low-acceleration regime, where modifications such as Milgromian dynamics (MOND) predict measurable deviations from Newtonian gravity. We construct a rigorous framework for conducting the wide binary test (WBT), emphasizing high quality sample selection, filtering of poor astrometric solutions, contamination mitigation, and uncertainty propagation. We show that undetected close binaries, chance alignments, and improper treatment of projection effects can mimic MOND-like signals. We introduce a checklist of best practices to identify and avoid these pitfalls. Applying this framework to Gaia DR3 data, we compile a high-purity sample of WBs within 130 pc with projected separations of 1 − 30 kAU, spanning the transition between the Newtonian and MOND regimes. We find that the scaled relative velocity distribution of wide binaries does not exhibit the 20% enhancement expected from MOND and is consistent with Newtonian gravity across all separations. A meta-analysis of previous WBTs shows that apparent MOND signals diminish as methodological rigour improves. We conclude that when stringent quality controls are applied, there is no observational evidence for MOND-induced velocity boosts in wide binaries. Our results place strong empirical constraints on modified gravity theories operating between a0/10 and 200 a0, where a0 is the MOND acceleration scale. Across this range of internal accelerations, Newtonian gravity is up to 1500 × more likely than MOND for our cleanest sample.

Copyright and License

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Acknowledgement

IB acknowledges support from Royal Society University Research Fellowship grant 211046. ZP acknowledges support from the European Research Council (ERC) grant 101002511. We thank the referee for their generous comments and suggestions.

Data Availability

The sample of WBs analysed in this study will be provided upon reasonable request to the lead author. All the data here was downloaded from the Gaia collaboration.2 It needs a login. The python code bynary is available for download and use by interested parties.3 Currently the software has only been installed on the ubuntu family of operating systems. Requests for support to install on other linux operating systems or other operating systems would be welcome. Please email the lead author with any questions.

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2602.24035 (arXiv)

Funding

Royal Society
211046
European Research Council
101002511

Dates

Submitted
2025-05-28
Accepted
2026-02-03
Available
2026-02-25
Published
Available
2026-03-11
Corrected and typeset

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