A recent study reveals that the orbital motions of widely separated binary stars, or “wide binaries,” break the standard model of gravity at low accelerations. By analyzing data from 26,500 containers across, the researchers found that accelerations of less than one nanometer per second squared deviate from Newton’s and Einstein’s laws of gravity.
A study of the orbital motions of large binaries found evidence that standard gravity decays at low accelerations. This discovery aligns with a modified theory called MOND and challenges current concepts of dark matter. The implications for astrophysics, physics, and cosmology are profound, and experts in the field have recognized the results as an important discovery.
A new study reports conclusive evidence that standard gravity breaks the low-acceleration limit, the result of a verifiable analysis of the orbital motions of widely separated, long-period binary stars. These stars are commonly known as wide binaries in astronomy and astrophysics. The study was conducted by Kyu-Hyun Chae, a professor of physics and astronomy at Sejong University in Seoul, and used up to 26,500 wide binaries within 650 light-years (LY), observed by the European Space Agency’s Gaia Space Telescope.
In a significant improvement over other research, Chae’s study focused on calculating the gravitational accelerations experienced by binary stars as a function of their separation, or equivalently, orbital period. This was achieved by a Monte Carlo deprojection of the observed motions projected onto the sky in three-dimensional space. Chae explains: “From the beginning, it was clear to me that gravity could be tested more directly and efficiently by calculating accelerations, because the gravitational field itself is an acceleration. My recent experiences investigating galactic rotation curves led me to this idea. Galactic disks and wide binaries share some similarity in their orbits, although wide binaries follow very elongated orbits, while hydrogen gas particles in a galactic disk follow nearly circular orbits. In addition, Chae calibrated the occurrence rate of hidden inner nested binaries to a baseline speedup, unlike other studies.
The study reveals that when two stars revolve around each other with accelerations of less than one nanometer per second squared, they begin to deviate from the predictions of Newton’s law of universal gravitation and Einstein’s general relativity. For accelerations less than about 0.1 nanometers per second squared, the observed acceleration is 30-40% greater than the Newton-Einstein prediction. The significance is considerable and meets the classic 5 sigma criteria for a scientific discovery. In a sample of 20,000 interval widths within a distance limit of 650 LY, two independent acceleration intervals show, respectively, deviations of more than 5 sigma significant in the same direction. Since the observed accelerations above about 10 nanometers per second squared agree well with the Newton-Einstein prediction from the same analysis, the observed increase in accelerations at lower accelerations is a mystery. Interestingly, this decomposition of the Newton-Einstein theory to lower accelerations was suggested 40 years ago by theoretical physicist Mordehai Milgrom of the Weizmann Institute in Israel in a new theoretical framework called Modified Newtonian Dynamics (MOND) or commonly used Milgromian Dynamics.
The amplification factor of about 1.4 is correctly predicted by a MOND-like Lagrangian theory of gravity called AQUAL, proposed by Milgrom and the late physicist Jacob Bekenstein. What is notable is that the correct amplification factor requires the external field effect of the Milky Way galaxy, a unique modified gravity prediction similar to MOND. Thus, the wide binary data indicates not only the breakdown of Newtonian dynamics but also the manifestation of the external field effect of modified gravity.
Of the results, Chae says: “It seems impossible that any unknown conspiracy or systematics could cause these gravity-acceleration-dependent standard failures according to AQUAL. I looked at all the possible systematics as described in the rather long article. The results are genuine. I anticipate that the results will be confirmed and refined with better and more important data in the future. I have also published all my codes for the sake of transparency and to serve any interested researchers.
Unlike galactic rotation curves, where the observed amplified accelerations can theoretically be attributed to dark matter in standard Newton-Einstein gravity, the broad binary dynamics cannot be affected even if it existed. Standard gravity simply breaks down to the weak acceleration limit as per the MOND framework. The implications of extended binary dynamics are profound for astrophysics, theoretical physics, and cosmology. Anomalies in Mercury’s orbits observed in the 19th century eventually led to Einstein’s general relativity. Now, anomalies in grand binaries call for a new theory that extends general relativity to the low-acceleration MOND limit.
Despite all the successes of Newtonian gravity, general relativity is necessary for relativistic gravitational phenomena such as black holes and gravitational waves. Similarly, despite all the successes of general relativity, a new theory is needed for MOND phenomena in the low acceleration limit. The low-gravity acceleration catastrophe may have some similarity to the ultraviolet catastrophe of classical electrodynamics that led to quantum physics.
Reference: “Standard Newton-Einstein Gravity Breakdown at Low Acceleration in the Internal Dynamics of Wide Binary Stars” by Kyu-Hyun Chae, Jul 24, 2023, The Astrophysical Journal. DOI: 10.3847/1538-4357/ace101