There are several mechanisms by which SMBHs can form binaries. One possibility is that they may form from the direct collapse of a gas cloud, without first forming individual stars. Another possibility is that they may form through the merger of smaller black holes, which themselves may have formed from the collapse of massive stars or through the merging of smaller black holes.
Finally, it is also possible that SMBHs may form through the capture of one SMBH by another. This could occur if two galaxies merge and their respective SMBHs end up on a collision course.
The existence of SMBH binaries has important implications for our understanding of the universe. For example, the presence of SMBH binaries can help to explain the origin of the jets of high-energy particles that are observed from some galaxies. SMBH binaries can also provide a source of gravitational waves, which are ripples in spacetime that are predicted by Einstein's theory of general relativity. The detection of gravitational waves from SMBH binaries would provide strong evidence for the existence of these systems and would allow us to study them in greater detail.
