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Solar sys. travel questions

  1. Mar 21, 2006 #1
    Hi All
    I have a few questions. Please correct me where needed. I'm new to posting here and have a basic understanding of astronomy.

    Question 1.

    The Solar system no doubt travels above and below the galactic plane as it makes it's way around. Do we know if there is say a sinusoidal rhythm to this travel and what would that period be?

    Question 2.

    Discover magazine reported the discovery of a galaxy that the Milky Way is in the process of consuming. Does anyone know if or when the solar system crosses the plane of this other galaxy?


  2. jcsd
  3. Mar 21, 2006 #2


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    1] If the solar system is in orbit around the galactic core, as is everything else, it will be an elliptic (nearly circular) orbit. So, it will rise and fall just once for every orbit - at its perihelion and aphelion, just like any other body does when orbiting its parent. I believe the only way it could do otherwise is if it is locked in a orbit with other, closer bodies such as a local cluster of stars.

    But this is overly simplifying. I expect that the movement of the SS around the galaxy is very complex and subtle, depending much more on local star densities than on an elliptical orbit.

    BTW, the galaxy makes one rotation about every 200My. The simple answer to your question is that it bobs up and down once every 200My.

    2] I believe that other galaxy has no disc to speak of; it is an elliptical (what's left of its original shape anyway).
  4. Mar 21, 2006 #3


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    Unlike a planet orbiting the Sun, the Sun actually crosses an ascending node and a descending node in its galactic orbit several times per orbit. I forget how many times. I think it crosses the galactic plane every 65 million years.
  5. Mar 21, 2006 #4


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    Hm. Yeah OK.

    I've been thinking - it probably interacts with the local spiral arm more than the galactic core, so I agree.
  6. Mar 22, 2006 #5
    I wonder if there is a relation of our systems travel around the galaxy to mass extinctions?
  7. Mar 22, 2006 #6


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    You are not the first person to wonder this. It's a theory that's been put forth.

    Google 'orion arm extinction'
  8. Mar 22, 2006 #7

    When the solar system moves up or down in the galactic plane it can cause objects orbiting the system to change direction (mostly objects on the outer edge of the system) as they interact with gravity from other systems. Some times those objects can be sent out of their current orbit, and they end up on a path that takes them through the relative center of the system. This leads to a greater posability of impacts, and could obviously lead to disaster for any planet in it's path. I believe it is one theory as to how the dinosaurs went extinct.
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