Spiral galaxy spin

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robina_williams

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Would the Milky Way be seen to spin in a clockwise direction if one were able to look down on it? Do all spiral galaxies have a clockwise spin?
 
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vogon13

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Depends on which side of the galaxy you are looking at.<br /><br />Galaxies are oriented (and spin) randomly.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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robina_williams

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Thank you. What if one were able to look down on the Milky Way from a position above the middle of the galaxy so that the whole galaxy was visible -- would it appear to spin clockwise?
 
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oscar1

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Again, from the top side or the bottom one? BTW, I wouldn't know what is top or what is bottom!
 
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kmarinas86

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www.worldalmanacforkids.com/explore/space/milkyway.html+"milky+way+rotates"+north<br /><br /><font color="yellow">Rotation.<br /><br />The Milky Way rotates around an axis joining the galactic poles. Viewed from the north galactic pole, the rotation of the Milky Way is clockwise, and the spiral arms trail in the same direction. The period of rotation decreases with the distance from the center of the galactic system. In the neighborhood of the solar system the period of rotation is more than 200 million years. The speed of the solar system due to the galactic rotation is about 270 km/sec (about 170 mi/sec).</font>/safety_wrapper>
 
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brellis

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I forget where I saw this: A few years back, a TV program showed a tantalizing computer graphic representation showing the rotation of the spiral arms of the Milky Way. <br /><br />The arms moved in some kind of orderly fashion, but many stars would trail behind, some actually moving in random directions relative to the motion of the spiral arms. <br /><br />They color coded the stars to signify those that were moving with the arm, those that were floating chaotically, and those that were moving in opposing or random directions due to collisions, etc. <br /><br />It was a really cool vid, I wonder if anyone knows where one might find such a representation online? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>
 
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robina_williams

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Thank you, brellis and kmarinas86, and the link leads to a fascinating article; the structure and rotation sections are particularly interesting. I wanted to give an idea of the direction of the rotation of the Milky Way's spiral arms for a fantasy book, and as far as I could tell, the direction was clockwise. This seems to fit with the linked piece, ie, clockwise direction from the north galactic pole. Thanks very much for the help -- it's appreciated.
 
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brellis

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hi robina<br /><br />i had a little time this morning to poke around the 'net, and i found some spots that describe why the arms of the galaxy move differently from the stars. As usual, when i speak conversationally about serious astronomy, i have just enough knowledge to drive off the cliff, so to speak, hehe.<br /><br />Here's a set of notes on the structure of the Milky Way. Excerpt here:<br /><br /><font color="yellow">Density wave theory: Spiral region of greater gravity concentrates stars and gas. The spiral regions rotate more slowly than the stars do (by about a half). Stars behind the region of greater gravity are pulled forward into the region and speed up. Stars leaving the region of greater gravity are pulled backward and slow down. Gas entering spiral wave is compressed. On downstream side of wave, there should be lots of H II regions (star formation regions). Unanswered questions: What forms the spiral wave in the first place? What maintains the wave?</font><br /><br /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>
 
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robina_williams

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Thanks for sending that link, brellis. That was kind of you. Very informative piece. Good questions you pose: what forms and maintains the spiral wave?<br />
 
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