  Supermassive black hole binaries (SMBHBs) may exist in the centers of
galaxies and active galactic nuclei (AGN) and are expected to be fairly common
in the Universe as a consequence of merging processes between galaxies. The
existence of SMBHBs can be probed by looking for double nuclei in galaxy
centers or, more easily, detecting periodic behavior in the observed radio
light curves. In a recent paper, Sudou et al. \cite{sudou2003} announced the
first direct observation of an SMBHB. Using VLBI observations they found that
the unresolved radio core of the radio galaxy 3C66B shows a well defined
elliptical motion with a period of $1.05\pm 0.03$ yrs, implying the presence of
a couple of massive black holes in the center of the galaxy. In the present
paper we study the astrophysical implications of the existence of such an SMBHB
in 3C66B. In particular we focus on the information that can be obtained from
detecting a signal periodicity either in the $X$-ray and/or $\gamma$-ray light
curves as a consequence of the motion of the black holes. These observations
could be used to extract further information on the physical parameters of the
SMBHB and partially solve the system parameter degeneracy. The detection of the
gravitational wave spectrum emitted by such system may be used to completely
determine the physical parameters of the binary system.
