LIGO Scientific Collaboration.
A reconstruction of the gravitational wave signal in the top panel compares observations from the LIGO detector in Livingston, La., in gray with a signal calculated from a numerical relativity simulation, in red. The time is counting down in seconds leading to the merger of the two black holes at zero. RIT researchers contributed to the simulations that reproduced the event and determined properties of the final black hole. The lower panel shows how the frequency of the gravitational waves changes with time and increases as the black holes spiral together. The black cross marks the point where the amplitude of the signal was largest and is approximately the time of the merger. The image was adapted from figure five in the upcoming LIGO paper in Physical Review Letters.