Final answer:
The merger of two black holes produces gravitational waves, which are ripples in spacetime, confirmed by LIGO observations according to Einstein's general theory of relativity.
Step-by-step explanation:
When a binary of two black holes merges together, the event does not produce a supernova, quasar, or pulsar, but rather gravitational waves. This phenomenon was predicted by Einstein's general theory of relativity and was confirmed by observations such as those carried out by the LIGO (Laser Interferometer Gravitational-Wave Observatory) which consists of two observing stations in Louisiana and Washington.
Gravitational waves are ripples in spacetime created by the acceleration of massive objects, and when black holes merge, they produce powerful bursts of gravitational waves, even though they do not emit light that we can see. The energy released in the form of gravitational waves during such a merger can be staggering, as it was with the first detection made by LIGO.
It is estimated that three times the mass of the Sun was converted to energy based on the equation E = mc², generating power about 10 times greater than all the stars in the visible universe, albeit briefly and imperceptibly to anything but the most sensitive detectors designed specifically to capture such events.