A groundbreaking study, based on observations from the European Space Agency’s billion-pixel Gaia space telescope, has revealed a “gravitational anomaly” that challenges our fundamental understanding of the universe. The anomaly occurs when loosely orbiting stars, known as wide binaries, seem to move in ways that defy standard models of gravity established by Albert Einstein and Isaac Newton.
Astronomer Kyu-Hyun Chae from Sejong University in South Korea made the discovery while studying binary star systems, which refer to two stars that orbit each other. At accelerations of lower than 0.1 nanometres per second squared, the orbit of the two stars deviated from Newton’s universal law of gravitation and Einstein’s general relativity.
The discovery puts into question the existence of ‘dark matter’ which was often used to explain such anomalies. “Testing gravity with wide binaries is interesting because dark matter can play no role in their internal dynamics,” Chae said.
Professor Chae theorised that a model known as Modified Newtonian Dynamics (MOND) could explain why these previous theoretical frameworks were unable to explain the stars’ movements. MOND was first conceptualised by Israeli physicist Mordehai Milgrom, who proposed a modification to the laws of gravity at low accelerations to explain observed irregularities in galactic rotation without the need for dark matter.
“Chae’s finding is a result of a very involved analysis of cutting-edge data, which, as far as I can judge, he has performed very meticulously and carefully,” said Milgrom, from the Weizmann Institute in Israel. “But for such a far-reaching finding – and it is indeed very far-reaching – we require confirmation by independent analyses, preferably with better future data.
“If this anomaly is confirmed as a breakdown of Newtonian dynamics, and especially if it indeed agrees with the most straightforward predictions of MOND, it will have enormous implications for astrophysics, cosmology, and for fundamental physics at large,” he added.
Professor Chae commented on the implications, asserting that potential systemic errors were rigorously examined and the results appeared to be genuine. He anticipates that the results will undergo further scrutiny and refinement as more data becomes available.
Nevertheless, these findings could have a profound effect on our conception of the universe. “Because the standard cosmology is based on general relativity, cosmology needs a major revision now,” Chae said. “I think we are now entering an extremely exciting period of time.”