Raver32 writes: "Small, ultrafaint "hobbit" galaxies recently found hovering around our Milky Way are comprised almost entirely of dark matter, a new study confirms. Dark matter is a mysterious substance scientists think accounts for most of the mass in the universe but that is invisible to current instruments. The finding, to be detailed in the Nov. 10 issue of Astrophysical Journal, could help resolve a cosmic accounting problem that has long vexed astronomers and also explain how such small galaxies form. According to the "Cold Dark Matter" model, which explains the growth and evolution of the universe, large galaxies such as our Milky Way should be surrounded by a swarm of up to several hundred smaller "dwarf" galaxies. However, until recently, only 11 such companion galaxies have been found. To explain this so-called Missing Dwarf Galaxy problem, theorists have suggested that the majority of dwarf galaxies contain very few, if any, stars and are instead made up mostly of dark matter."