Wide binaries in ultra-faint dwarf galaxies as a probe of extended dark objects

Wide stellar binaries are sensitive dynamical probes of dark matter substructure. We generalize existing point-mass disruption constraints to spherical extended dark objects and apply the resulting framework to the population of. The new analysis still awaits peer review, but it already lays out the central claim clearly.

That matters because cosmology operates at the edge of what current instruments can measure, where systematic errors and model assumptions are never trivial. Small discrepancies between independent measurements have historically pointed toward missing physics rather than simple calibration errors, and the ongoing tension in the Hubble constant is a live example of how a persistent disagreement between methods can reshape the theoretical landscape. Each new dataset that approaches this territory with independent systematics adds real information to a problem that has resisted easy resolution for more than a decade. Wide stellar binaries are sensitive dynamical probes of dark matter substructure. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy.

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We generalize existing point-mass disruption constraints to spherical extended dark objects and apply the resulting framework to the population of wide-binary candidates. We derive 95% confidence limits on the dark matter fraction as a function of the perturber mass, the radius enclosing 90% of the mass, and the density profile, considering.

Sufficiently compact objects converge to the point-mass limit, whereas finite size suppresses binary disruption when the perturber becomes comparable to the relevant encounter and. The constraints remain sensitive to dark matter fractions well below unity over a broad region of the mass-radius plane and extend to objects substantially larger than those.

The relevance goes beyond one dataset because even small shifts in measured parameters can matter when the field is testing the limits of the standard cosmological model. The Lambda-CDM framework describes the observable universe with remarkable economy, but its success rests on two components, dark matter and dark energy, whose physical nature remains entirely unknown. Any credible measurement that tightens or loosens the constraints on those components moves the entire theoretical enterprise forward, regardless of whether the immediate result looks dramatic on its own terms.

As an application, we map the r^-3/2 results onto ultracompact minihalos and derive an illustrative constraint on the primordial curvature power spectrum. Ultra-faint-dwarf wide binaries therefore offer a purely gravitational probe of the abundance of extended dark matter objects and of the small-scale primordial curvature power.

Because this is still a preprint, the result should be read with genuine interest and proportionate caution. Peer review is not a guarantee of correctness, but it is a process that forces authors to respond to technical criticism from specialists who have no stake in a particular outcome. Preprints that survive that process, often with substantive revisions, emerge with a stronger evidential base than the version that first appeared. Until that stage is complete, the responsible reading keeps uncertainty explicitly visible rather than treating the claims as established findings.

The next step is to see whether the effect survives when independent surveys, different calibration strategies and tighter control of systematic uncertainties enter the picture. Programmes such as Euclid, DESI and the Rubin Observatory will deliver datasets over the next several years that cover the same parameter space with largely independent methods. If the current signal persists through those tests, its theoretical implications will become impossible to set aside. Until peer review and independent follow-up address those open questions, skepticism is not a failure of appreciation for the work; it is part of how science decides what to keep.

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