The centers of galaxies are mysterious places since their cores are hidden from view by tightly packed stars and thick gas and dust. But within the last decade, as radio and visible images are studied together, astronomers are finding that most galaxies harbor humongous black holes in their centers.

This is a radio image of a strange galaxy, Cygnus A, the second brightest radio source in the sky. At 700 million l-y distance, the galaxy producing these jets are not seen with visible light. In fact, the radio emission was found before the visible galaxy was. The radio light here is being emitted by electrons spiraling around vast magnetic field lines and moving at relativistic speeds, about 50% of the speed of light. A suitably massive black hole in the core of this galaxy would be able to produce such explosions.