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Rotation Of Spiral Galaxies

  1. Mar 9, 2006 #1
    Obivously, the direction of the rotation of a Spiral Galaxy depends on the vantage point from which you look at it. From Earth, do all Spiral Galaxies rotate in the same direction? Or, because the universe is so vast, the rotation direction is irrelevant and has morre to do with prior collisions?
  2. jcsd
  3. Mar 10, 2006 #2


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    I'm not aware of any preferred rotational direction, or axial inclination of spiral galaxies.
  4. Mar 10, 2006 #3

  5. Mar 10, 2006 #4


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    If they did, it would be a very serious violation of the cosmological principle (the universe would be heavily anisotropic) and you'd hear about it.
  6. Mar 13, 2006 #5
    Thank You Chronos, K-86 and Space Tiger but....

    This leads me to a more focused and possibly silly question.......
    Can a Spiral galaxy have a Top and a bottom- Top being the face of the super massive blackhole'e opening meaning the bottom is the opposite side?

    If so, do sprials rotate based on their supermassive bh's rotation and do they all rotate in the same direction?
  7. Mar 14, 2006 #6
    Black holes don't have tops or bottoms. Remember, black holes are matter that have been compressed to a radius at which the escape velocity is greater than the speed of light. The use of the word "hole" in the name is misleading.
  8. Mar 14, 2006 #7


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    (Non-rotating) black holes are spherically symmetric; they appear the same in every direction. As Markjdb said, they don't have "tops" or "bottoms" or "openings." Anything can fall into a black hole from any direction. They're spheres.

    And no, there is no preferred direction from which to view a spiral galaxy. They'd look pretty much the same from either side.

    Since the entire galaxy coalesced out of a large cloud of gas, you'd expect that all rotations within the galaxy would be in the same direction -- the black hole would rotate in the same direction as the material which has fallen into it and "donated" its angular momentum -- but catastrophic events like galaxy collisions and mergers can probably create more unusual situations.

    Galaxy formation is not entirely understood yet, but (if I recall correctly) spirals are thought to not have undergone collisions or other interactions. Spirals are relatively "undisturbed," while lenticular and irregular galaxies are left in the aftermath of an interaction.

    - Warren
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