What two black holes merging into one looks like

Advanced LIGO saw gravitational waves from two black holes that merged over a billion light years from Earth. This computer simulation shows (in slow motion) what this would look like up close. If this movie were played back in real time, it would last for about one third of a second. In this movie, the black holes are near us, in front of a sky filled with stars and gas and dust. The black regions are the shadows of the two black holes: no light would reach us from these areas. Light from each star or bit of gas or dust travels to our eyes along paths (light rays) that are greatly bent by the holes' gravity and by their warped spacetime. This is called "gravitational lensing." Because of this gravitational lensing, the pattern of stellar and gas/dust images changes in fascinating ways, as the black holes orbit each other, then collide and merge. The ring around the black holes, known as an "Einstein ring," arises from all the stars in a small region directly behind the holes; gravitational lensing smears their images into the shape of a ring. The gravitational waves themselves would not be seen by a human near the black holes (though they would be felt!) and so do not show in this video, with one important exception: The gravitational waves that are traveling outward toward the small region behind the black holes disturb that region’s stellar images in the Einstein ring, causing them to slosh around in the ring, even long after the collision. The gravitational waves traveling in other directions cause weaker, and shorter-lived sloshing, everywhere outside the Einstein ring.