Solar systems in a galaxy

Discussion in 'Astronomy, Exobiology, & Cosmology' started by timojin, Mar 21, 2017.

  1. timojin Valued Senior Member

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    Do solar system in a galaxy have a fixed position ?
    Do the solar systems migrate in a fixed direction direction ?
    Are solar systems kept at given distances from its neighbor solar system ?
     
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  3. Janus58 Valued Senior Member

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    No, No, and No.
    When we look at our neighboring stars they have all different proper motions and radial velocities.
    For example, the Alpha Centauri system has a radial velocity of 21.4 km/sec towards us and a proper motion of 3679.25 milliarcseconds RA and 473.67 milliarcseconds Dec per year. This means is is moving at ~31 km/sec at an angle of ~47 degrees from the line of sight to it and that it will pass as close as 3.14 light years from us at some future date (as compared to its present distance of 4.3 light years.)

    Each system follows its own orbit through the galaxy in response to the gravity of the galaxy as a whole. Our own solar system "bobs'' above and below the galactic plane periodically in its orbit.
     
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  5. timojin Valued Senior Member

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    Why are you saying NO , NO .NO
    So Alpha centauri is moving toward us , So it have an orbital motion ?
    I will assume that our solar system might have a similar motion within the galaxy ?
    Are we moving in the same direction or opposite ?
    Will it be that at some point in time one of the a centauri or b centaury will be close to our planets ?
     
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  7. DaveC426913 Valued Senior Member

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    You're reading too much into this.

    You asked three questions. He politely answered all three. He did not YELL, he provided a grammatically correct list as an answer.
     
  8. DaveC426913 Valued Senior Member

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    Maybe, yes, yes, same.

    A Centauri has motion around the galaxy, as do we.
    Same direction.

    Hard to say, but unlikely.

    A. Centauri is 4 light years away. Our solar system is only 5.3 light hours in radius.

    Place two marbles on a bumpy playground, 87 metres (260 feet) apart. Set one rolling in the general direction of the other. How likely are they to collide?
     
    Last edited: Mar 22, 2017
  9. timojin Valued Senior Member

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    What do you want me to do , walk away. We are talking science , there are continuous questions, do you have anything to offer ?
     
  10. DaveC426913 Valued Senior Member

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    Sorry, we're crossing signals here.

    You said "Why are you saying NO , NO .NO"
    You capitalized NO three times, suggesting that you thought he was "yelling" at you in frustration.
    He wasn't; he was simply answering your questions very curtly. Then he elaborated. It's a common response format when presented with a list of several questions.
    No offense was intended by him (or by me).

    I did.

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  11. timojin Valued Senior Member

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    I suppose you meant within the domain of our Milky way galaxy.
    I did not imply collision,
    I believe there must be some order , otherwise the galaxy would fall apart. Is not that is what supposed to do the Dark matter ?
     
  12. Janus58 Valued Senior Member

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    1,801
    The difference is that our system and Alpha Centauri have orbits with slightly different radii, eccentricities and inclinations. [/quote]
    Are we moving in the same direction or opposite ?
    [/quote] Roughly the same direction relative to the center of the galaxy. The Sun's orbital velocity through the galaxy is ~200 km/sec, Alpha C's motion relative to us is a bit better than 1/6 of that. [ quote]
    Will it be that at some point in time one of the a centauri or b centaury will be close to our planets ?[/QUOTE]
    No, the 3.14 light year distance will be the closest approach.
    In fact, in about 33,000 years, Alpha C will not even be the closest system. Ross 248, a small Red dwarf which is ~10 light years distant now, will be. Ross 248 will pass at just a bit over 3 light years before receding again.
     
  13. Janus58 Valued Senior Member

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    1,801
    For a good idea of the relative motions of neighboring stars you can check out this star mapper from the European Space Agency.
    http://sci.esa.int/star_mapper/
    Once it finishes loading, choose the motion option at the bottom and then hit the play button. This is what the motions of the stars would look like from Earth when sped up to a high time rate.
    You also have the option of viewing the constellation lines, but they become quite unrecognizable after a very short time.
    Here's an example I made by overlaying four screenshots of the mapper, showing Orion at ~100,000 yr intervals.
    Note how some of the stars have moved very little while others a fair amount. This is mainly due to the difference in distance between the individual stars and ourselves. Closer stars will show a much larger proper motion than further stars will even if their relative motion with respect to us are about the same.

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    Here's the same view at ~1,000,000 years from now. Parts of the constellation haven't changed much, but others have greatly. In addition, stars from other constellation have moved enough that The lines from these constellations cross over Orion and each other. A person dividing the stars into constellations at this point in time would be creating ones that would be totally different than those we use today, and wouldn't even group the same stars together.

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  14. DaveC426913 Valued Senior Member

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    Nor do I mean collision. I am simply pointing out the vast distances involved when talking about whether two systems will be in close proximity.

    Well, of course there's some order. We're all orbiting the centre of the galaxy, in the same direction. There is some local proper motion ,but it's not much to fuss over.
     

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