Key Points
- A new 3D velocity method provides direct gravity measurement in wide binary stars.
- The method surpasses older 2D-based models by incorporating full velocity data.
- Initial findings suggest gravity is 40–50% stronger than Newtonian predictions at low acceleration.
- The deviation has high statistical significance (4.2σ), aligning with MOND theory.
Astrophysicist Kyu-Hyun Chae from Sejong University has developed a groundbreaking method for measuring gravity using full 3D velocity data of wide binary stars, opening new avenues in the study of gravity at extremely low accelerations. Published in The Astrophysical Journal, the method uses Bayesian analysis and Markov Chain Monte Carlo simulations to derive the probability distribution of a gravity parameter, bypassing the limitations of earlier 2D statistical techniques.
Wide binaries—stars separated by more than 2,000 astronomical units—experience internal gravitational accelerations lower than 1 nanometer per second squared. These conditions make them natural testbeds for gravity beyond the classical Newtonian framework. Chae’s new method leverages all three velocity components, including the challenging-to-obtain radial velocities, to achieve higher precision in testing gravitational theories.
The first application of this technique involved analyzing about 300 wide binaries using data from the European Space Agency’s Gaia mission. While Gaia’s radial velocity measurements are less precise than its positional data, the results are consistent with predictions from modified Newtonian dynamics (MOND). This theory proposes deviations from Newton’s laws at low accelerations.
The analysis found that while Newtonian gravity holds at higher accelerations (above 10 nm/s²), it deviates significantly, by 40–50%, at lower accelerations. This deviation corresponds to a statistical significance of 4.2σ, implying a 99.997% probability that the deviation is real and not due to chance.
Experts in the field have praised the work. Xavier Hernandez called it “a rigorous Bayesian approach,” and Pavel Kroupa noted that it “advances the study of gravitation to a new level.” Milgrom, the originator of MOND, emphasized that such anomalies cannot be explained by dark matter, further supporting the need for new physics.
With new precision data from instruments like GEMINI’s MAROON-X and ongoing studies to rule out hidden third stars, decisive conclusions about the nature of gravity may soon be within reach.
