GW170104: Third direct detection of gravitational waves

The Advanced LIGO detectors registered in the 4th of January 2017 a merger of a black hole binary system of masses approx. 30 and 20 Solar masses and a formation of a remnant black hole of 49 solar masses and spin parameter of about 0.64, at a distance of about 880 Mpc (corresponding to a redshift z = 0.18). It is likely that at least one of the black holes was spinning opposite the direction of the binary orbit. This is the first detection to show evidence for such a spin configuration. The detection was also used to test the general theory of relativity and to estimate the graviton mass.