What happens to a black hole when it collides with another black hole? This new model shows you closely. The question of just what could possibly happen when two black holes come across at a very close distance is one that we've been involved with for a while. But, even still we understand a little about how the whole procedure might go down in theory as the two black holes merge, what we actually haven't identified is how it would look like.
A new study paper displayed on ArXiv by a team of scientists directed by Cornell University's Andy Bohn proceeds on just that question. Although other efforts at picturing the procedure have done a good job, they haven't considered how the movement of light through space-time and the physics of visualization would come organized to generate the visual. Here is what the published paper says:
“In this paper, we focus on the question of what an observer in the vicinity of a BBH would actually see as the black holes orbit, spiral inward, and merge, with an example shown in figure 1. This is in contrast to most BBH visualizations, in which the positions or horizons of the two black holes are simply shown as a function of time in some coordinate system. We instead compute the paths of light rays that enter the observer's eye or camera to find what would actually be seen. Furthermore, this path must be computed in the fully time-dependent space-time, as the orbital velocities for a black-hole binary are typically large enough that the system cannot be approximated as time-independent during the time taken by the photons to travel across it.”
After producing a model that better accounts for the properties of gravitational lensing on the eye of the observer, the group produced the image above of two black holes merging, located near our own Galaxy Milky Way. You can also read the whole paper here.