Abstract

Recent statistical analyses of wide binaries have revealed a boost in gravitational acceleration with respect to the prediction by Newtonian gravity at low internal accelerations ≲ 10−9 m s−2 . This phenomenon is important because it does not permit the dark matter interpretation, unlike galaxy rotation curves. We extend previous analyses by increasing the maximum sky-projected separation from 30 to 50 kilo astronomical units (kau). We show that the so-called “perspective effects” are not negligible at this extended separation and, thus, incorporate it in our analysis. With wide binaries selected with very stringent criteria, we find that the gravitational acceleration boost factor, γg ≡ gobs/gN, is 1.61+0.37 −0.29 (from δobs−newt ≡ (log10 γg)/ √ 2 = 0.147 ± 0.062) at Newtonian accelerations gN = 10−11.0 m s−2 , corresponding to separations of tens of kau for solar-mass binaries. At Newtonian accelerations gN = 10−10.3 m s−2 , we find γg = 1.26+0.12 −0.10 (δobs−newt = 0.072 ± 0.027). For all binaries with gN ≲ 10−10 m s −2 from our sample, we find γg = 1.32+0.12 −0.11 (δobs−newt = 0.085 ± 0.027). These results are consistent with the generic prediction of MOND-type modified gravity, although the current data are not sufficient to pin down the low-acceleration limiting behavior. Finally, we emphasize that the observed deviation from Newtonian gravity cannot be explained by the perspective effects or any separation-dependent eccentricity variation which we take into account.