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[1105.1873] Wide binaries as a critical test of Classical Gravity
 
Authors:X. Hernandez, M. A. Jimenez, C. Allen
Abstract:Assuming Newton's gravity and GR to be valid at all scales, leads to the dark matter hypothesis as a forced requirement demanded by the observed dynamics and measured baryonic content at galactic and extragalactic scales. Alternatively, one can propose a contrasting scenario where gravity exhibits a change of regime at acceleration scales a<a0, and obtain just as good a fit to observations across astrophysical scales. This modified regime at a<a0 will generically be characterised by equilibrium velocities which become independent of distance, regardless of the details of the modified gravity theory in question. Here we identify a critical experiment in this debate offered by wide orbit binary stars. Since for 1 M0 systems the acceleration drops below a0 at scales of around 7000 AU, an statistical survey of wide binaries with relative velocities and separations reaching beyond 10^4 AU should yield a conclusive answer to the above debate. We perform such a study using first a recent catalogue of wide binaries from the {\it Hipparcos} satellite having high signal to noise relative velocity measurements. The experiment is repeated using a more extensive low signal to noise wide binary catalogue from the ground based Sloan Digital Sky Survey. Results from both samples are compatible, showing clearly an 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<a0 acceleration regime. Our results are strongly suggestive of a breakdown of Kepler's third law precisely below a0 scales, precisely as predicted by modified gravity theories designed not to require any dark matter at galactic scales and beyond.
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Maciej Bilicki



Joined: 12 May 2010
Posts: 19
Affiliation: University of Cape Town

PostPosted: August 24 2011  Reply with quote

The authors claim to have detected an upper limit to the relative velocities in wide binary star systems, independent of separation for over three orders of magnitude, as predicted by modified gravity theories.

I'd be interested in opinions on that. Stars are not a usual cosmologist's specialty, so I can't really judge. I wonder, provided these measurements are correct, if one can still try to save dark matter as the factor responsible for this phenomenon.
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