Galaxies can create many of the same stellar stream distortions that astronomers have looked to as possible signs of dark matter.

Astronomers have long hoped that gaps, bends, and other distortions in long bands of stars around the Milky Way could reveal the hidden influence of dark matter. But new simulations suggest many of those features can arise from the galaxy itself, even without the small dark matter clumps thought to produce them.

University of Washington researchers modeled roughly 15,000 of these bands, known as stellar streams, across four Milky Way-sized galaxies. The simulations omitted small dark matter clumps called subhalos. After five billion simulated years, irregularities appeared in nearly every stream, and only 70 remained perfectly smooth.