Milky Way gravity may mimic dark matter effects in star streams

New simulations suggest that irregularities in star streams orbiting the Milky Way may be caused by the galaxy's own complex gravitational field rather than by concentrations of dark matter.

Astronomers have long used star streams—long, thin structures of stars formed when clusters are pulled into the galaxy—as potential detectors for dark matter. It was previously hypothesized that gaps, bends, or breaks in these streams were ‘scars’ left by gravitational encounters with invisible dark matter subhalos.

However, research from the University of Washington indicates that the Milky Way's own gravity can produce similar disruptions. By simulating galaxies without dark matter concentrations, researchers observed that the galaxy's inherent gravitational irregularities can mimic the effects previously attributed to dark matter, complicating efforts to use star streams as a reliable tool for mapping the invisible substance.