Like the saturn ring, why isn’t it surround the whole planet or the general shape of milky way galaxy is pretty much like a disc
Or the solar system
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The simplest answer to this is that the planet is spinning. It resists its own gravity around it’s equator because of centrifugal force. This small bulge is going to tug ever so slightly at orbits above and below it, over a long enough time frame it will bring the relatively small mass of the particles in the belt in to an equatorial orbit.
Edit: and we can actually harness this process to do what’s called a sun-synchronous orbit, using the extra bulge and it’s tug to keep an orbit precessing around a body. https://en.wikipedia.org/wiki/Sun-synchronous_orbit
[Here’s a good video about it.](https://www.youtube.com/watch?v=tmNXKqeUtJM) It’s easier to understand with the graphics. But the basic reasons why spiral galaxies, planetary rings, and even the way all the planets travel around the sun on a mostly flat plane has to do with gravity vs angular momentum. Particles are attracted by gravity, and they also have angular momentum from being pulled by this gravity around the source. How that gravity is distributed will influence how the particles are moving. So if you have a mass of particles going in a lot of directions, they will all be pulled towards the center of where they all are because that’s the center of the gravity for the system. As they collide together, they eventually all balance out into a disk, which is what we see in something like a planetary ring.
If you wet a ball and spin it fast, the water will move to the middle and if you hold it over a piece if paper, the drops that are flung off will be in a line.
Once you get your head around the fact that all these planets are spinning around relatively fast, and the galaxy is essentially just the same thing on a much larger scale, it makes sense. The matter gets flung around like the drops coming off a ball
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