Two additional dwarf galaxies that appear to be satellites of Andromeda, the closest spiral galaxy to Earth, have been discovered by researchers are the University of Michigan.
Invisible to the naked eye, at 1.1 million and 600,000 light years from Andromeda, these are two of the furthest satellite galaxies ever detected.
The prevailing hypothesis is that visible galaxies are all nestled in beds of dark matter, and each bed of dark matter has a galaxy in it. For a given volume of universe, the predictions match observations of large galaxies.
But this hypothesis breaks down in relation to smaller galaxies, with models predicting far more dark matter than observed galaxies.