Astron. J. 137, 3009–3037 (2009)

A leading theory for the evolution of the Universe's structure explains how lumpy galaxies formed after matter was evenly distributed by a relatively smooth Big Bang. 'Cold dark matter' models predict that there should be many more small dwarf galaxies surrounding the Milky Way than have been identified. Kristin Chiboucas of the University of Hawaii in Honolulu and her colleagues think that the 'missing galaxy' problem is not just local; they report a paucity of dwarfs around Messier 81 (M81), a spiral galaxy in the constellation Ursa Major (the Great Bear).

A dozen of the 22 new dwarfs the team found lie within M81's gravitational influence. Theory predicted hundreds more. This finding adds weight to the evidence that missing dwarfs are a real problem and not one of imperfect observation.