# What is the structure of an event horizon for colliding black holes?

I would suspect that two black holes within close vicinity of one another would warp each other's event horizons such that the Schwarzchild's radius would no longer apply.

Do the event horizons remain intact, during and after a collision or is there an intermediate, more complex structure?

What is the structure, process of singularities merging?

• Relevant buzzword: "ringdown" (to Kerr) – Danu Feb 13 '16 at 17:31
• look at the webcast of the announcement . youtube.com/watch?v=_582rU6neLc there is a mathematical model . the complete black is where the horizon starts. 7' 45'', – anna v Feb 13 '16 at 17:42

Stage 1

At this stage, the two black holes begin to spiral inward, slowly, but the closer they get to each other, the faster their spin.

Stage 2

Then the outer parts of the hole start to form a dumb-bell shaped, but the horizons haven't touched each other yet.

Stage 3

As the spinning gets faster and faster, the hole starts to give out gravitational waves, slowly giving out the spin energy. At the same time, the horizons have just touched and merged into a giant dumb-bell shaped horizon.

Stage 4

The gravitational waves will gradually carry away the energy, leaving a smooth, no-hair, spinning, Kerr black hole.