Why are our planets and galaxy in a plane shape?

In summary, the planets in our solar system are spread out in a plane due to the conservation of angular momentum in a rotating mass. Similarly, our galaxy is also in the shape of a plane because it is the most 'economical' shape for conservation of angular momentum during its formation. However, our understanding of the formation of disk systems is still incomplete. Without any angular momentum or with collisionless particles, a sphere shape would be formed, while heavily interacting particles with high angular momentum would result in a disk shape. The explanation given by Space Tiger, as mentioned in a previous thread, is the most accurate and concise explanation for this phenomenon.
  • #1
syano
82
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Why are the planets in our solar system spread out in a plane instead of being more randomly spread around the Sun? And why is our galaxy in the shape of a plane instead of all the stars in our galaxy being more randomly spread around the middle of our galaxy?

Thanks,
 
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  • #2
As Space Tiger explained in a different thread, a disk is the most 'economical' shape for conservation of angular momentum in a rotating mass. When the initial gas cloud was coalescing, therefore, it would naturally settle in that way.
 
  • #3
Here's the thread:

https://www.physicsforums.com/showthread.php?t=93098&highlight=disk"

Keep in mind that we still don't have a complete understanding of the formation of real disk systems, but it's best just to think of these as "minimum energy conditions". With no angular momentum or with collisionless particles, you will tend to get a sphere. With heavily interacting particles that have a lot of angular momentum, you tend to get disks.
 
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  • #4
Thanks yet again, Mr. Tiger, for setting things straight. While astrophysics is one of my favourite things in life, I really have no education at all in it. It's always a pleasure to read your posts and further my knowledge. Cheers, bud.
edit: So what happened to my edit in the previous post where I said that ST's explanation was better?
 
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1. Why do our planets and galaxy appear to be in a flat, disk-like shape?

The reason for this is due to the way planets and stars form. As a cloud of gas and dust collapses under its own gravity, it begins to spin faster and faster. This spinning motion causes the material to flatten into a disk shape, much like a spinning pizza dough flattens out into a disk. This is known as the accretion disk theory.

2. What causes the planets and stars to all orbit on the same plane?

This is a result of conservation of angular momentum. As the spinning disk of gas and dust collapses, it causes the material to spin in the same direction. As the material continues to collapse, it becomes more compact and begins to rotate faster, resulting in all the planets and stars orbiting on the same plane.

3. Is there any significance to the fact that our galaxy is in a flat, disk-like shape?

There are several theories about the significance of this shape. Some scientists believe that it is necessary for the stability and longevity of the galaxy. Others suggest that it may be a result of the interactions between our galaxy and other galaxies in the universe.

4. Are there any other galaxies that are not in a plane shape?

Yes, there are galaxies that do not have a flat, disk-like shape. These are known as irregular galaxies and they can have a variety of shapes and structures. However, it is still unknown why some galaxies have a more chaotic structure while others have a more organized, disk-like shape.

5. How does the plane shape of our galaxy affect our view of the universe?

The plane shape of our galaxy can have an impact on our view of the universe. Since we are located within the disk of our galaxy, it can be more challenging to see objects that are outside of this plane, as the light from these objects can be obscured by the gas and dust in the disk. However, this also means that we have a clearer view of objects that are within the same plane as us, such as the stars and planets in our own solar system.

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