Gaia Data Delivers Blow to Choice theories, Bolsters Dark Matter Case for Milky Way
Toulouse, France – New research leveraging data from the European Space Agency’s Gaia satellite is challenging long-held alternative theories to dark matter, providing the strongest evidence yet that our galaxy’s structure aligns with predictions based on the existence of this elusive substance. A team at the IRAP institute in Toulouse has found that the speed of stars decreases with distance from the galactic centre – a finding incompatible with modified Newtonian Dynamics (MOND), a popular alternative to dark matter, but consistent with dark matter models.
For decades, the nature of dark matter – the invisible substance believed to make up roughly 85% of the universe’s mass – has remained one of astrophysics’ biggest mysteries. While undetectable directly, its gravitational effects are widely observed. MOND, proposed in the 1980s, attempts to explain thes effects by modifying the laws of gravity at very low accelerations, eliminating the need for dark matter. However, the new findings cast serious doubt on its applicability to our own galaxy.
“This behavior is a game-changer,” says Even Coquery, one of the study’s authors.
The breakthrough stems from Gaia’s unprecedented mapping of over a billion stars in the Milky Way since 2013. By comparing actual stellar velocities to theoretical models, the Toulouse team discovered that only the model incorporating dark matter accurately reproduces the observed decline in stellar speed as distance from the galactic center increases.
A key issue for MOND lies in its reliance on a single, universal constant applicable to all galaxies.To fit the Milky Way’s observed rotation curve, this constant would need to be drastically different than predicted, undermining the theory’s foundational principle. Researchers state that, at least for our galaxy, MOND ”no longer works.”
“This revelation doesn’t mean everything is solved,” the researchers acknowledge, “but it strongly weakens alternatives to dark matter.”
While dark matter remains invisible and its composition unknown, the study reinforces its position as the most robust model for explaining galactic gravitational behavior. The Milky Way, it appears, may now serve as a crucial “laboratory” for further examination. Each new observation, like those provided by Gaia, refines our understanding and brings scientists closer to unlocking the secrets of this fundamental component of the universe.
