Why is our galaxy planar?

  1. Why is our galaxy planar? Why isn't it spherical?
     
  2. jcsd
  3. chroot

    chroot 10,426
    Staff Emeritus
    Science Advisor
    Gold Member

    Because it has rotational kinetic energy -- it's spinning.

    - Warren
     
  4. SpaceTiger

    SpaceTiger 2,977
    Staff Emeritus
    Science Advisor
    Gold Member

    Though it's worth mentioning that the process by which it obtained that rotation is still relatively unclear. Our best theory at the moment is that it was due to tidal torques from other pre-collapse galaxies.
     
  5. tony873004

    tony873004 1,584
    Science Advisor
    Gold Member

    I think its more spherical than it looks. There's lots of dark matter in the halo.
     
  6. SpaceTiger

    SpaceTiger 2,977
    Staff Emeritus
    Science Advisor
    Gold Member

    That depends on what you're referring to. The dark matter distribution is indeed thought to be spherical (roughly), but the gas is clearly in a disk. The fact that the dark matter is non-interacting means that it wouldn't be able to organize itself into a disk structure despite having non-zero rotation.
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?