The cross marks the location of the black hole Cygnus X-1 in this radio image. The bright region to the left (east) of the black hole is a dense cloud of gas existing in the space between the stars, the interstellar medium. The action of the jet from Cygnus X-1 has 'blown a bubble' in this gas cloud, extending to the north and west (right) of the black hole. Image Credit: Gallo et al., Westerbork radio telescope
