Einstein's general theory of relativity suggests, among other things, that masses in space distort the geometry of space-time. In addition, moving objects emit waves of gravitational radiation that carry energy away into space.
Black hole? Or wormhole in disguise? | CosmOnline
The Oth Dimension 4 Pics
How Galaxies are Classified by Type (Infographic) by Karl Tate, Infographics Artist