Super massive black hole binaries are believed to form during galaxy mergers.
(The star age puts the planet age as older than the galaxy merger.)
However, galaxy mergers were much more common long ago when they were closer together, because the expanding universe was smaller.
Computer simulations are often the only means to study stellar collisions, galaxy mergers, as well as galactic and black hole interactions.
It is currently thought that cD's are the result of galaxy mergers.
LBG-2377 is the most distant galaxy merger ever discovered, at a distance of 11.4 billion light years.
This galaxy merger is so distant that the universe was in its infancy when its light was emitted.
The spin-flip could have been caused by absorption of a second black hole during a galaxy merger.
In this model, a galaxy merger causes a second, smaller supermassive black hole to be deposited near the center of the original radio galaxy.
Another likely place to find a HCSS would be near the site of a recent galaxy merger.