The Dark Matter Halo is a huge area and volume of space at the edges of our galaxy that seems likely to be full of Dark Matter. Of course, we can't see the Dark Matter, but we can see it's gravitational affects on the way our Milky Way Galaxy rotates.
It's estimated to be the largest percentage of our galaxy. It ranges from 100,000 to 300,000 light years from the Galactic Center. For comparison, our sun is only about 25,000 light years from the Galactic Center. So, the halo starts at a point 4 times as far from the center as we are, and is freakin' huge.
Game and Story Use
- The Dark Matter Halo may serve as some type of barrier keeping things in their own galaxies.
- The exact properties of the Dark Matter Halo will of course be defined by what type(s) of Dark Matter it is composed of. Could be Black Holes, Brown Dwarfs, Subatomic Particles, or something completely new we haven't imagined yet.
- A halo of dark and dying stars might be an untapped resource which can be mined by a civilization that's on the cusp of attaining a Type III classification on the Kardashev scale. Once they'd depleted that, though, it's out into the vasty deep void.