In the theory of superstrings (super due to the addition of supergravity) D-branes are compactified on a circle. We know, theoretically, that D5 is compactified to give us electromagnetism. Then there is the M-theory that gives us D11 as supergravity. Now the only question I have, which I have searched for and cannot find, is what does D8 give us? Now as a warning, please ignore my basic terminology. I am not an expert in this field and will never claim to be. I just am curious to see if anyone knows.