A new study published on May 19, 2025, in *Physical Review Letters*, challenges existing assumptions about the mass of ultralight bosonic dark matter particles. Led by Tim Zimmermann from the University of Oslo, the research establishes a new lower bound for the mass, suggesting it must exceed 2.2 × 10⁻²¹ electron volts (eV).
The team's analysis focused on the internal motions of stars within Leo II, a satellite galaxy of the Milky Way. Using a tool called GRAVSPHERE, they derived 5,000 possible dark matter density profiles by comparing them with profiles generated by quantum wave functions of various dark matter particle masses. The study concluded that if the particle is too light, quantum fuzziness spreads it too thinly, preventing it from forming the observed structures.
This new mass limit is over 100 times greater than previous estimates based on the Heisenberg uncertainty principle. These findings have significant implications for popular ultralight dark matter models, particularly fuzzy dark matter, and provide a more robust constraint on the properties of bosonic dark matter, relying only on stellar kinematics and quantum mechanics.