Dark matter distribution around the Milky Way galaxy, Segue 2 highlighted. Source
Back in 2007, a tiny galaxy was discovered orbiting the Milky Way galaxy (our galaxy). Containing somewhere around 1,000 stars this galaxy is the smallest yet discovered. Our current models of the universe predict that we should find many of these dwarf galaxies, but our previous inability to detect them has thrown some doubt on our theories. The detection of this new galaxy offers us some insight into the origin of the universe and may back up our models.
A paper is being published that talks about this galaxy and the "dark matter halo" that it finds itself trapped in, but that stuff is beyond me, so I won't embarrass myself trying to explain it.