The first sighting of clustered dwarf galaxies bolsters a leading theory about how big galaxies such as our Milky Way are formed, and how dark matter binds them, researchers said on January 23.
Theorised but never seen, the bundled galaxies were discovered using the largest optical survey of the night sky ever compiled, they reported in the journal Nature Astronomy.
Seven clusters of three-to-five galaxies are each 10 to 1,000 times smaller than the Milky Way.
