I understand that the Milky way is a spiral galaxy with a supermassive black hole in the center.
I understand that because of the stress-energy and the gravitational field of the black hole, the center is rotating faster then the outer parts, and that gives the galaxy a spiral shape.
Question: 1. Let's say the black hole in the middle would suddenly disappear. How long would it take for the Earth and other parts of the galaxy to stop moving in spirals? So how long would all the planets follow the geodesics created by the black hole's gravity, and when would all the Solar systems start to fly away?
- What shape would that galaxy be?