Detection of Gravitational Anomaly at Low Acceleration from a Highest-quality Sample of 36 Wide Binaries with Accurate 3D Velocities

We set out to accurately measure gravity in the low-acceleration range (10-11,10-9), m, s-2 from 3D motions of isolated wide binary stars. Gaia DR3 provides precise measurements of the four sky-plane components of the 3D relative displacement and velocity (r, v) for a wide binary, but not comparably precise line-of-sight (radial) separation and relative velocity v r. Based on our new observations and the public databases/publications, we assemble a sample of 36 nearby (distance <150 pc) wide binaries in the low-acceleration regime with accurate values of v r (measurement uncertainty < 100 m,s-1). Kinematic contaminants such as undetected stellar companions are well under control using various observational diagnostics such as Gaia's ruwe parameter, the color-magnitude diagram, multi-epoch observations of radial velocities, Speckle interferometric follow-up observations, and requiring Hipparcos-Gaia proper motion consistency. For the parameter Γ 10 sqrtγ with γ G/G N (where G is a parameter generalizing Newton's constant G N in elliptical orbits), we find Γ=0.102-0.021+0.028 for <10-9.1, m, s-2 (0.132-0.027+0.035 for <10-9.5, m, s-2) giving a gravity boost factor of γ=1.60-0.14+0.24, which rules out Newton and is higher than relevant MOND predictions. This strong anomaly is dominated by two systems (the pairs of HD 189739, HD 189760, and TYC 259-236-1, TYC 259-906-1) that have 3D relative velocities exceeding their estimated Newtonian escape velocities but are unlikely to be chance associations or contaminated systems. (abridged)