University of Washington study suggests Milky Way gravity may mimic dark matter signatures

New research from the University of Washington suggests that irregularities in stellar streams—long, thin trails of stars orbiting the Milky Way—may not always indicate the presence of dark matter. Astronomers have traditionally used gaps, kinks, and clumps in these streams as evidence of invisible dark matter subhalos passing nearby and exerting gravitational influence.

By simulating approximately 15,000 stellar streams across four Milky Way-sized galaxies, researchers found that realistic galactic gravity can produce complex structural variations, such as bends and wiggles, even without encounters with dark matter. The study, published in The Astrophysical Journal, revealed that after five billion years, only about 70 of the 15,000 simulated streams remained featureless. These findings suggest that astronomers must account for the Milky Way’s own gravitational effects to avoid mistaking them for dark matter signatures.