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What effects do the collision of galaxies have on the solar system?

  1. Dec 6, 2006 #1
    Because if would seem to me, that planets suffer relativly little disturbance from these collisions, that is, they're not pulled away from their main star, by other massive objects passing nearby. (Or in most cases they're not) During the 4 billion year history of our solar system, the Earth and other planets seem to have remained attached to this system, in which time it would of seen a
    few major mergers between galaxies.

    What are your thoughts or have you come across anything that supports this theory, or possibly suggests something else?
     
  2. jcsd
  3. Dec 6, 2006 #2

    chroot

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    The gravitational pull of other galaxies is billions and billions and billions of times smaller than the gravitational pull of the nearby Sun.

    Let's do a simple Newtonian calculation:

    This is the force exerted on the Earth by the Sun:

    http://www.google.com/search?hl=en&...earth))+/+(1+astronomical+unit)^2&btnG=Search

    This is the force exerted by a 100 million solar-mass galaxy, 4 billion light-years away:

    http://www.google.com/search?hl=en&...rth))+/+(4+billion+light+years)^2&btnG=Search

    Note the exponent. The force due to the Sun is 22 orders of magnitude larger. Also, note that the force exerted on the Earth by the distant galaxy is approximately the same force that a heavy book exerts on a table while resting there. It's insignificant.

    - Warren
     
  4. Dec 6, 2006 #3

    chroot

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    And, in case you're talking about galaxies colliding with the Milky Way, you may also be in for a surprise: the average distance between stars doesn't really change that much even when galaxies are colliding. Very few stars every come close enough (while travelling slowly enough) to become gravitationally bound with each other.

    - Warren
     
  5. Dec 6, 2006 #4
    I should of been a bit clearer when I said "massive objects passing nearby" I didn't mean the gravitaional pull of a galaxy millions of light years away, but stars, black holes, and other massive objects that would pass close to the solor
    system. And yes, I had already known that stars would pass by eachother relatively freely during mergers, but on the off chance that one did pass close enough, I thought it was plausible that it could capture planets, until you pointed out the speed difference would make it unlikely.

    Thanks
     
  6. Dec 6, 2006 #5

    russ_watters

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    Sky and Telescope magazine had a pretty good article on our impending collision with Andromeda a few months ago.
     
  7. Dec 6, 2006 #6

    SpaceTiger

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    It's worth remembering that even stars in our own Milky Way have non-negligible peculiar velocities (tens of km/s) that can, on rare occasions, bring them close together. Close encounters that would have a noticable effect on planetary orbits are very rare (and may never have happened), but any reasonably close encounter (~0.1 parsec) can cause a disturbance of the outer Oort Cloud, perhaps sending comets into the inner solar system.
     
  8. Dec 6, 2006 #7
    ...increasing the probability of mass extinction. Darn.
     
  9. Dec 7, 2006 #8

    Chronos

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    Galaxies are pretty diffuse objects when it comes to stellar density. They can pass through each other with little effect on dense objects, like stars and planets. Gas clouds are, however, a different matter. Many cosmologists suspect such collisions play a major role in starbursts.
     
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