A black hole X-ray binary (BHXB) is a black hole orbiting a normal star. When matter from the normal star accretes onto the black hole, a jet of charged particles is ejected at relativistic (near-light) speeds, and these particles emit strong X-ray radiation. The processes involved are thought to be similar to ones active under the more dramatic conditions in active galactic nuclei. Most known BHXBs are located in our galaxy, and being much closer to us they can be studied in more detail than their more distant cousins.