A perplexing "break" in a stream of stars around the Milky Way could be the result of dark matter — that is, if the mysterious cosmic stuff interacts with itself.
The feature in question is in the GD-1 stellar stream, a thin group of stars moving together on a shared trajectory through the Milky Way's all-encompassing halo. The GD-1 stellar stream has been well-studied by astronomers, but a gap in its structure has long been a puzzle.
