When Black Holes Collide

Explanation: What happens when two black holes collide? This extreme scenario likely occurs in the centers of some merging galaxies and multiple star systems. The featured video shows a computer animation of the final stages of such a merger, while highlighting the gravitational lensing effects that would appear on a background starfield . The black regions indicate the event horizons of the dynamic duo , while a surrounding ring of shifting background stars indicates the position of their combined Einstein ring . All background stars not only have images visible outside of this Einstein ring , but also have one or more companion images visible on the inside. Eventually the two black holes coalesce . The end stages of such a merger may provide a strong and predictable blast of gravitational radiation , a much sought after form of radiation different than light that has never yet been directly observed.

Space Music Video: APOD images from September 2015