We have a few models about how black holes might merge. The best model was that a massive binary star might end their lives as a pair of black holes, then spira

We have a few models about how black holes might merge. The best model was that a massive binary star might end their lives as a pair of black holes, then spiral down into each other. In this model, there will not be any optical counterpart to the merger. But this model can't explain all of the observations by LIGO. When a star ends its life as a black hole, there's a cap on how large the black hole can be; if you make stars larger than that, they end their lives prematurely in pair-instability supernova, which do not leave behind black holes. But LIGO saw black hole mergers where the constituent black holes were larger than that maximum mass, up to twice as large. Binary black hole mergers can't explain those observations. The next idea on the drawing board was that there could be a dense swarm of stars, black holes, and neutron stars in the accretion disks around quasars. In this model, the black holes can grow in the accretion disk, and they can undergo multiple mergers and get much larger. However, when they merge, the new combined black hole should be kicked through the accretion disk at an odd angle, and steal some of the material into a new, more chaotic accretion disk. This new accretion disk should produce a temporary flare up, and then more periodic flareups every few months as the new black hole oscillates up and down through the accretion disk. The new black hole should eventually get dampened into a nearly circular, in-spiraling orbit, where it is available for a subsequent merger. This new observation, if it's confirmed, lends a lot of support that the second model happens too, and teaches us a lot about what exactly is happening around supermassive black holes. So the takeaway from this article isn't just "hey, we saw this cool thing", it's "hey, we saw this thing that increases our understanding" which IMHO is a hell of a lot cooler. The title implies the former, which annoys me. Hopefully, we'll see periodic flareups around the quasar, which would largely confirm the model.