What determines the direction the "disk" shape faces of galaxys and solarsystems?

[Banshii]

What determines the direction of the gravitational field (the direction the "disk" around an object faces) of something other things orbit... such as a solar system or galaxy? For example, if I am in space and am looking forward, one galaxy might look like it's sitting horizontal according to my position, while the one next to it may be verticle. Does it have to do with only gravity? Or does magnetism come into play... like does it have to do with where the magnetic poles are of the center object.

[ACG52]

It has to do with nothing at all except random chance.

[pwagen]

There's no up or down in space. When we perceive a galaxy as vertical, that's arbitrary based on which way is up to us.

[Banshii]

Yes I realize that pwagen. That's why I stated relative to how I am facing. But anyways, why do galaxys look like a flat shape instead of everyting orbiting randomly. Why isn't it a ball shape? What makes it choose a particular orbiting path? ACG52, if it really is random, and have nothing to do with the poles, why does each object orbiting around something stay on the same line, causing it to look flat?

Edited April 5, 2013 by Banshii

[swansont]

It has to do with any motion present at the formation. Angular momentum is conserved, so any present is going to remain, unless there is some external torque is applied to change it. Orbits are going to be roughly in a plane because otherwise you get collisions more often, which tends to destroy the objects not orbiting in that plane.

[Enthalpy]

Objects going in random directions interact often, be it by shocks or by gravitation, and they lose their random speed through inelastic shocks or - in elastic interactions like gravitation - because some objects acquire energy and leave the galaxy while the others loose energy; that would be the equivalent of evaporation that cools a liquid.

 

Beware this is how I believe to understand it; it may not be standard science.

 

The mean rotation momentum however is preserved as this one creates no collisions, just a general movement, which survives over this evolution and gives the disk its diameter while interactions reduce the thickness. The direction of the initial mean momentum determines the orientation of the disk.

 

I also imagine that small plentiful objects interact often and can also get or loose more energy if meeting heavier objects, so they "condense" faster to the disk than heavier objects do - so you get gas, dust and individual stars in the disk, while heavier objetcs like globular clusters stay for long in the halo.

 

As well, distance is important, with (not too) centrical objects grouping in the plane faster, while more distant ones stay longer at random. Similar to our Solar system and Oort's cloud.

 

Again, I may be horribly wrong.

 

Beware as well that galactic dark matter plays the main role in the formation and evolution of galaxies but its distribution and properties are badly known...

 

Fresh science: small satellite galaxies in our neighbourhood are to be in the plane of giant galaxies, and not at random as previously thought.

 

Did I read that irregular galaxies result from galactic collisions?

Edited April 6, 2013 by Enthalpy