A ghostly ribbon of stars reveals hidden dark matter

A faint ribbon of stars around a distant galaxy has become the first globular cluster stellar stream ever identified beyond the Milky Way. Because the stars trace the galaxy’s gravity, researchers used the stream to estimate how much invisible dark matter surrounds it and how that matter is distributed. The breakthrough offers astronomers a promising new way to investigate one of the universe’s greatest mysteries. An international research team, including an astrophysicist from Northwestern University, has identified the first stellar stream of this type ever observed outside the Milky Way. Astronomers have long predicted that such streams should exist around ... [6094 chars]