Dwarf galaxies shed light on dark matter

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 Monday. Seven clusters of three-to-five galaxies are each 10 to 1,000 times smaller than the Milky Way. "We suspect these groups are gravitationally bound and thus will eventually merge to form one larger, intermediate-mass galaxy," said lead author Sabrina Stierwalt, an astrophysicist at the National Radio Astronomy Ob