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Space Science

Spiral Galaxy Spins the Wrong Way 51

Posted by chrisd from the galactic-spirograph dept.
Ant writes: "The New Scientist has an article about a galaxy in the constellation Centaurus is puzzling astronomers by spinning in the wrong direction. NGC 4622 has bright twisting arms containing newborn stars and lies 111 million light years away."
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Spiral Galaxy Spins the Wrong Way More

Spiral Galaxy Spins the Wrong Way

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  • Wrong way? (Score:2, Interesting)

    by SpaceLifeForm ( 228190 )
    It could be two galaxies that happen to be lined up from our point of view.
    Space can be tricky, there is more there than meets the eye.

    • Re:Wrong way? (Score:3, Insightful)

      by taion ( 304184 )
      You should read the article more carefully before you comment next time.

      If you did, you'd clearly have noticed that the article said that the outer spiral arms pointed in the direction that they were rotating, and that was the peculiar aspect of this galaxy, not the actual direction of rotation itself.

      • Re:Wrong way? (Score:2, Interesting)

        by SpaceLifeForm ( 228190 )
        I read the article carefully. My point was that it appears to be strange. If one galaxy is rotating clockwise (from our perspective), and another (either in front or behind but lined up with the first) is rotating counter-clockwise (from our perspective), and at the large distance involved, and the lack of accuracy in measuring such distances, there actually may be nothing strange going on at all. The spiral arms that appear to moving in the unexpected direction may actually belong to the other galaxy than the one that was apparently observed. The article infers that the two galaxies have collided, but they actually could just be close enough to each other to give the observed results. 111,000,000 lightyears is a long way away. I'll not go into gravitational lensing which can throw any galactic observation into doubt.

        • Re:Wrong way? (Score:5, Informative)

          by taion ( 304184 ) on Saturday February 09, 2002 @03:45AM (#2978458) Homepage
          You're continuing to misinterpret the article. The statement was that, for normal galaxies, the spiral arms trail the direction of rotation. That is, if the galaxy itself is rotating "clockwise", the spiral arms trail behind in a "counterclockwise" fashion.

          However, in this case, the spiral arms lead in FRONT of the galaxy's rotation. That is, if the galaxy is rotating "clockwise", the arms stretch forward in the "clockwise" direction; if the galaxy is rotating ccw, the arms also stretch forward ccw!

          The actual direction of rotation of the galaxy is irrelevant, the unexpected fact was the orientation of the spiral arms of the galaxy relative to the galaxy itself. Even in the event of an overlay, the rotation of the spiral arms in the unexpected direction could still be clearly observed.

          In your given case, with two galaxies possessing "normal" behaviour, the arms on both galaxies would trail in the direction of the rotation. If they were spinning in opposite directions, then which arm belonged to which galaxy would be entirely evident through the direction in which the spiral arms were rotating.

          Your objections, then, are entirely groundless.

          But I suppose we can just blame the editors for the vague title.

      • Re:Wrong way? (Score:2, Informative)

        by CheshireCatCO ( 185193 )
        There is a legitimate question here, and it's the subject of some tricky observing and analysis. You can get the Doppler map of the galaxy, by you need to work out which it is tipping towards you in order to work out if it is a leading or trailing arm spiral. It's hard to say if the "top" of the galaxy is nearer or us or the "bottom" is. If you can't tell that, you can't tell which way it is spinning.

        The usual way of guessing at this it to look for globular clusters. The side that is nearer us will have fewer gobulars in front of it than the farther side. But this is a guess, of course. With a nearly face-on galaxy, this difference is harder to pick out.

    • Re:Wrong way? (Score:4, Informative)

      by kittenslietome ( 319948 ) <[slashdot.org] [at] [genkisugi.net]> on Saturday February 09, 2002 @06:44PM (#2980395) Homepage
      Here [ua.edu] is a link to the guy's site--much more information and should be read before anybody starts making-up explanations.

  • CNN Article (Score:4, Informative)

    by Eigenray ( 317237 ) on Friday February 08, 2002 @10:47PM (#2977862)
    CNN has an article [cnn.com] with more information.

  • alright (Score:4, Funny)

    by nomadic ( 141991 ) <`nomadicworld' `at' `gmail.com'> on Friday February 08, 2002 @11:48PM (#2978013) Homepage
    I think it's time we wrote our local congresspeople to get this remedied.

  • ... (Score:4, Funny)

    by questionlp ( 58365 ) on Saturday February 09, 2002 @12:20AM (#2978082) Homepage
    That galaxy must be in the southern hemisphere of the universe?

  • Reverse Time (Score:1, Interesting)

    by Anonymous Coward
    The flow of time in that part of the universe "backwards" to the flow of time in our part of the universe.
    • If it was, would the galaxy be emiting light normally? I would think time flowing backwards would make very strange things happen optically. And what about the area in between, at what point do you leave "normal" time and enter "backwards time, and what heppens when you do? I would think it would be an impassible barrier to even light. Think about it, if light left normal space into space with backwards time, it would immediatly reverse direction wouldn't it? And as it came back into normal space it would reverse again. It would essentially be traped at the boundry. I can't think of a way that time could flow in a different directions in 2 parts of the universe without very strange easily observeable consequences.
      • your assuming that time is either forwards or backwards, yes or no, one or zero. what if the intermediate boundary was like a gradient? or analog as opposed to digital.

        just jabbering...

  • Article in The Sun Newspaper Online (Score:2, Informative)

    by Anonymous Coward
    The Sun Newspaper Online has a worth and informative article [thesun.co.uk] about this discovery in its Science section.

  • Is it that weird? (Score:3, Informative)

    by CheshireCatCO ( 185193 ) on Saturday February 09, 2002 @01:47PM (#2979539) Homepage
    I'm a bit confused at why anyone this that this is so bizzaire. Sure, most galaxies are trailing spirals, but there are enough leading spirals to make them not freakish. I'd suspect that it is the spin put on the story by the media, but one astronomer is quoted calling leading-arm spirals extremely rare.

    My take on this is that the real news is the evidence of disruption/interaction. We've seen that before (M51, the Whirlpool, is a good example), but it's still a damned cool thing to see.

  • More math is needed (Score:3, Informative)

    by Daniel Dvorkin ( 106857 ) on Saturday February 09, 2002 @03:57PM (#2979934) Homepage Journal
    Says the math geek, I think this is as much of a mathematical problem as an astronomical one -- i.e., we really don't have a good grasp of the dynamics of galaxy formation, and we won't until the math is there. Classical Newtonian orbital mechanics doesn't do it, of course, since it's an n-body problem with a very, very large value of n. Some new kind of analytical technique needs to be invented before we can say we know much about why galaxies look and move the way they do.
    • The 3-Body problem cannot, in general, be tackle analytically (Poincare showed this). So I am hesitant to believe that we will ever have an analtical technique to directly handle a billion-body problem, like galaxies.

      That said, we *do* have analtic techniques to examine galactic dynamics. Lots of 'em, ranging from fluid discriptions to wave approximations. But stunning coinidence, I was just reading Binney and Tremaine, a whole text on galactic dynamics. (The physics is pretty much the same as in planetary rings.) So lots of math exists to tackle these problems. As a math major in astro. grad school, I am pretty confident when I say that the mathematicians won't need to cook up new tools as much as we need to figure out how to apply the existing ones.

      The other approach is, of course, various simulation techniques, mainly N-body codes. For that we need
      a) Faster computers. We always want faster computers.
      b) Better algorithms. This is a place with the Applied Math folks would be really helpful.
    • What we really need is more data. Various examinations of the winding problem have been made, and most reasonable solutions lead to very tightly wound spiral arms, if there are any at all. We don't see this, though. We now have this galaxy with arms "trailing" in the same direction as its motion...

      Hopefully we'll be able to take this and turn it into a more accurate model of what a galaxy IS so that we can then figure out why it DOES what it does.

      • We have data: lots of pictures of pretty spiral galaxies. You yourself point out the problem: we can't explain those data.

        Shameless plug for my own work: maybe Saturn's rings will provide a suffient analog to further our understanding. Cassini arrives in 2 years for some up-close views of what's happening.
  • Maybe that Galaxy is standing still, or spinning very slowly, and we are spinning the wrong way?
  • Maybe they're looking at it upside down? :)

  • What this shows.... (Score:1, Interesting)

    by Anonymous Coward
    is that there is more to a galaxy than what we can see, i.e. dark matter. Have you noticed that the time it takes the outside of the galaxy to orbit the core is the same as the inside? Normal physics, assuming what's lit is what we can see, would say that the outside would have to orbit much, much slower to not overpower the galaxy's gravity. But they don't, meaning some other source of mass must be both moving with the arms to keep them up, and providng the gravity necessary to keep them in. Otherwise, the core would rotate very quickly, and you would get what happens when you swirl chocolate milk mix in with milk, it'd blend. Not only does that not happen, but there are barrel-arm galaxies whose arms stick straight out, and now, galaxies whose arms point the direction they're going.

    I think this just shows even more convincing evidence for dark matter. By exemplifying this galaxy, we can show that there has to be something else there preventing the arms from "oozing" behind the rotation of the galaxy.

    Chocolate milk: explains all, even mysteries of the universe
    • You're right up until you state that the core must rotate more quickly. Dark matter has nothing to do with the core of the galaxy or its rotation. And even if the core did rotate rapidly, a la stars about a black hole, so what? There wouldn't be any radial mixing from that, as long as the orbits were Keplerian and nearly circular (which they are, as far as I've heard).

      I also fail to see why this result indicates the presence of dark matter. The direction of rotation should not depend on the dark matter content. This is about how the galaxy formed and how the spiral arms were generated, not about what the galaxy is made of.
    • hmmmm.....Dark Matter...God's invisable paper-mache'.

      Jaysyn

  • Time (Score:2, Interesting)

    by sean23007 ( 143364 )
    Maybe they made a mistake in the measurements, and as they graphed the rotation of the galaxy time was actually going backwards in their simulation. That would yield the results we see now, in a much more humorous (in a slap-yourself-in-the-face kind of) way.
  • They just realized that they were looking at the photographs upside down :)
    • Actually, if would be more accurate to say that they were looking out from the piece of paper that held the photograph to get the images they were seeing.

      An upside down spiral is still a same arm direction spiral.
  • It am Bizarro Galaxy. Everything am different in Bizarro Galaxy. For example, me am happy in job and relationship; am handsome, too.
  • So this is where antimatter comes from...

  • For about two seconds, I thought:

    "Ooooh! Ooooh! Maybe someone engineered that as visible proof of their presence!"

    Then I thought:

    "But that would only be a slight probability if it was the only one,"

    And it wasn't. And then I thought:

    "what if several civilizations had the same idea at the same time?"

    Could you imagine how pissed you'd be if you went to all that trouble to stand out and two guys down the block did the same thing? :)

    Idle thinking, like idling at a stoplight, burns fuel and gets you no-where. But then again, stopping and starting at every stoplight wastes even more fuel and puts more wear on the engine so... I wonder where I was going with that?

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