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Astronomers Solve Magnetic Fields Mystery

Posted by timothy on from the let's-say-this-beach-ball-is-your-head dept.

An anonymous reader writes "It is a long-standing and unsolved mystery why 80% of all planetary nebulae are not spherical. Theories suggest that magnetic fields play a role in shaping planetary nebulae. A team of astronomers from Germany has now discovered the first direct clue that magnetic fields might indeed create these remarkable shapes. Planetary nebulae are expanding gas shells that are ejected by Sun-like stars at the end of their lifetimes."

43 of 159 comments (clear)

  1. What about the other 20%? by DominoTree · · Score: 4, Interesting

    If 80% aren't spherical one must ask why the other 20% are NOT.

    1. Re:What about the other 20%? by Anonymous Coward · · Score: 3, Funny

      I would suggest those 20% aren't not not perfectly spherical, but that magnetic forces have figured less into their formation for one reason or another (less iron present?) so they wound up being less not spherical than the other 80%.

    2. Re:What about the other 20%? by Triddle · · Score: 3, Interesting

      Perhaps the other 20% are just bipolars we happen to be seeing end on...

    3. Re:What about the other 20%? by StarsAreAlsoFire · · Score: 3, Interesting

      The warping is symmetrical, in 3 (4?) dimensions -- unless there is significant spin. 'Significant' depends on the masses in question.

      Which, now that I think of it that way, begs the same question as yourself, rephrased; does frame dragging affect the shape of galaxies? Perhaps helping align galaxies with the spin plane of a massive central black hole? Hm. I am guessing that a bunch of things are helping towards the same end.

      Frame dragging is also symmetric, but only in the plane of rotation; and since we are talking about the curious fact that most galaxies are not symmetric in 3 dimensions....

      And how is that for a non-answer!?

    4. Re:What about the other 20%? by kfg · · Score: 5, Insightful

      No, no, no. Mass causes the warping of space which causes gravity, not gravitational "distortions" and the inverse square law still holds just as it does for the Newtonian model; relativistic gravity "looks" the same as Newtonian from any dirction.

      As it must, because we can see that gravity does and one expects, in the absence of other forces, for phenomenon such as planetary nebulae to be symetrical.

      By the way, you might be interested to know that the density of material in a such a nebula may well be lower than in an earth bound, artificial vacuum chamber. They may look massive from here, but that's because we see the entire mass of the florescing gases from a distance. If we were in the middle of it it might well look like empty space.

      Think of a hazy day. You're not in a fog at all and it's only when you try to look across great distances that you realize the air isn't "empty."

      KFG

    5. Re:What about the other 20%? by kettlechips · · Score: 3, Interesting

      Since the non-sphericalness is supposed to be caused by a magnetic field, it can be inferred that the involved star's magnetic field isn't particularly strong in the case of "The other 20%".
      As the article mentions, it turns out that the observed stars had magnetic fields many times stronger than our sun's.
      Whether the 80-20 ratio is realistic remains to be seen, but in essence it would simply depend on the strength of a particular star's magnetic field.

    6. Re:What about the other 20%? by kfg · · Score: 4, Funny

      dude, this guy is dumb.

      Nah, just ignorant. He's heard stuff he doesn't understand. Ignorance is curable. Stupid is in the bones.

      Note that he was smart enough to phrase his post as a question asking for clarification, which, given the nature of this forum, also implies a certain amount of self worth without lapsing into egotism.

      I'm the damed fool who was stupid enough to make statements. That sort of behaviour can get you garotted around these parts.

      KFG

    7. Re:What about the other 20%? by orthogonal · · Score: 5, Funny

      If 80% aren't spherical one must ask why the other 20% are NOT.

      Why even bother to ask why? If you come across something and you can't figure out how it could have occurred, just claim the event or process is the product of Intelligent Design .

      Why spend year after tedious year engaging in reductionist scientific inquiry when you can just bail out immediately with an answer that cannot be falsified: Intelligent Design .

      Worried that your invisible sky-ghost or imaginary all-powerful personal friend isn't getting the deferential worship He deserves in this age of secular humanism? Sneak your sky-ghost back into the schools and indoctrinate another generation of devout sheep with Intelligent Design .

      Remember the "Argument from Personal Incredulity": if you're too thick to figure out how something works, it must be because no one can figure it out! Don't sweat it! Just explain it away by saying it was caused personally God^H^H^H an Intelligent Designer!

      Don't waste time asking question or doing science! Just give credit to an Intelligent Designer and go back to sleep!

      --
      Opinions on the Twiddler2 hand-held keyboard?
    8. Re:What about the other 20%? by Zoinks · · Score: 3, Interesting

      In fact, a better question to ask now is, do stars with spherical nebulae exhibit a strong magnetic field? The results reported were on the basis of asymmetrical nebulae, and in each case, evidence of a strong magnetic field was detected.

      The article also states that the astronomers' next step is to try to detect magnetic fields around the stars that have spherical nebulae. If they find none, I would say this pretty much clinches the conclusion, at least until some other unexplained effect is discovered.

      To directly address your question, if strong magnetic fields are the reason for asymmetric nebulae, then we should ask why do 20% of stars have a weak magnetic field? (Or, conversely, why do 80% of stars have a strong field)

  2. More and more by adennis · · Score: 3, Insightful

    "The First Direct Clue" While this may seem monumental, there will be many, many more clues and each will most likely lead the researches to a completely different conclusion.

    1. Re:More and more by marevan · · Score: 2, Insightful

      Yeah the topic in this is missleading. They haven't solved anything, just had a major clue. However, as far as I'm concerned, in universal scope one can never have facts, just theories which work in certain fields, until they are replaced by more accurate theories.

  3. Great by pronobozo · · Score: 2, Funny

    Now explain why the magnetic fields are shaped that way. :-)

    --
    ------
    insert sig here,here, and here
    1. Re:Great by polysylabic+psudonym · · Score: 2, Insightful

      I know you're joking but there's a serious question there which some may seriously wonder about. Magnetic fields by their nature repel others of the same polarity. You can think of the fields as rubber bands or strings reaching from a north pole to a south pole and pushing away from each other. You can see a better description and a picture (of magnetic field lines - not galaxies) here.

  4. this about that by djupedal · · Score: 2, Funny

    [clip] has now discovered the first direct clue that magnetic fields might indeed create these remarkable shapes

    When pushed for an explanation of why the crab nebula was so different, one scientist responded with a huff and withdrew into his basement office.

    In other news...

    A couple in the Hamptons has asked the same group of scientists to determine why socks dissapear in the dryer. Film at eleven.

    1. Re:this about that by Triddle · · Score: 4, Informative

      The crab is a supernova remnant, not a planetary nebula.

    2. Re: this about that by Black+Parrot · · Score: 5, Funny


      > A couple in the Hamptons has asked the same group of scientists to determine why socks dissapear in the dryer.

      They disappear into the electronic equivalent of a black hole, and re-appear on the internet as sock puppets.

      --
      Sheesh, evil *and* a jerk. -- Jade
    3. Re:this about that by krymsin01 · · Score: 2, Funny

      You are wrong! The turtle steals my socks. Turtles all the way DOWN!

      --
      stuff
    4. Re:this about that by ine8181 · · Score: 2, Interesting

      Ah, but planetary nebulae have little to do with planets at all. It's a misleading name that got stuck to them because they resembled big planets (or something like that).

      Planetary nebulae and supernovae remnants would differ in their origin -- the former from red giants and the latter from supernovae (duh), the size, obviously, shape (explosion cloud vs. ejected atmosphere), and the source of radiation that illuminates the nebulae... but I'm not sure how.

      Supernovae remnants would have neutron stars in the middle, but what's in the planetary nebulae? anyone?

    5. Re:this about that by Eric604 · · Score: 2, Informative
      Supernovae remnants would have neutron stars in the middle, but what's in the planetary nebulae? anyone?

      a white dwarf according to this page

    6. Re:this about that by CheeseyDJ · · Score: 2, Informative

      The remnant in the middle of a planetary nebula is a sphere of incredibly hot solid helium (mostly), which used to be the core of the star (i.e. where the fusion actually took place).

      It is called a white dwarf at this stage, and as it has no power source (just residual heat) it eventually cools over an extremely long time to become a black dwarf.

  5. What about the color intensity? by Man+in+Spandex · · Score: 2, Interesting

    Is it the magnetic fields also that makes it so in a nebula, a part of it can look more red than another. Let's say in one part of a nebula, the field is stronger and more matter/gas is attracted within that field (if thats how it works.) would that then create all the variations of whichever color that the star creates depending on how and how much gas is spreaded throughout the field?

    1. Re:What about the color intensity? by StarsAreAlsoFire · · Score: 5, Interesting

      Most (all?) photos you are likely to see of nebula are enhanced, and thus the colors generally vary depending on what the 'artist' (astronomer) was studying; colors that highlight differences in density will be used by the astronomer studying gas density, colors that accentuate gas temperature by the astronmer studying gas dynamics, etc.

      That isn't to say your argument is wrong in anyway. I would agree with your hypothesis; however am not an expert in nebula dynamics in any way shape or form. I will state with great certainty that IF there are significate magnetic forces within a nebula, you WILL see higher gas densities along the magnetic lines of force -- the same idea as when you have iron filings on a sheet of paper and put a magnet under it: those filings will align with the field lines of the magnet.

      This could be an interesting topic (the whole tread). I hope some good answers come out of it!

    2. Re:What about the color intensity? by Abcd1234 · · Score: 3, Informative

      Well, it's partly that, but keep in mind, planetary nebula are very much three-dimensional objects. For example, the Ring Nebula is actually, in all probability, more or a barrel shape like the Butteryfly Nebula. However, because we're seeing it edge-on, we see it as a ring, rather than it's true shape. And the result is color concentration on the edges.

      Similarly, some of the perceived complexity in objects like the Ant Nebula may be due to perspective, as we see it from an angle.

      And speaking of the Ant Nebula, as is mentioned in the APOD article, another likely contributing factor to nebular complexity is the presence of other bodies orbiting the new white dwarf, such as a companion star or planetary body. These objects likely manipulate the shape of the nebula via gravitational or electromagnetic forces.

  6. this is nice to see by BoomTechnology · · Score: 2, Informative

    I have to say it's nice to see magnetic fields getting more praise than usual! All my professors tell me is "magnetic fields aren't important and blah blah blah so don't worry or care about them" ... then again I'm currently majoring in Electrical Engineering. :) It will be great to see what else unfolds in terms of the importance magnetic fields play in the structure of the universe!

    --
    Now then, Dmitri, you know how we've always talked about the possibility of something going wrong with the Bomb...
    1. Re:this is nice to see by Anonymous Coward · · Score: 2, Insightful

      Magnetic fields not important in EE??? Ever heard of a transformer?

    2. Re:this is nice to see by pe1rxq · · Score: 2, Informative

      An EE that dismisses magnetic fields is a crap EE.
      Hint: Electric and magnetic fields are kind of related, try creating a current without either one of them.

      Jeroen

      --
      Secure messaging: http://quickmsg.vreeken.net/
    3. Re:this is nice to see by wass · · Score: 2, Interesting
      Considering that electronics engineers study a *lot* more than just transformers, I'd say that the EE's opinion on the matter is justified

      Considering everyone reading this article is using a computer with some form of magnetic storage, I'd say he's got a valid point.

      Ferromagnetism is way too prolific in magnetic storage, so I'll ignore that and talk about other magnetic effects. Magnetism is directly tied to any inductive element in a circuit, and manifests itself through self and mutual induction. Eg, a signal-carrying wire has a non-zero self inductance based on its geometry.

      Design of circuit elements at GHz frequencies requires minimizing inductance (usually by making things as small as possible), or carefully designing inductive elements, which would otherwise attenuate higher-frequencies and thereby limit the component bandwidth. And on the other hand, inductors are very useful in filter design, one fairly common item being an RF choke. But they're usually avoided by microwave or RF engineers. As my old boss said when we were considering using inductors to try to calibrate out a certain nonlinearity in a GHz-bandwidth circuit "Engineers usually avoid inductors because they don't understand them."

      So besides magnetic storage, magnetic fields are employed in transformers, as the parent said, which are used in almost all AC-powered devices. Then there are electric motors and dynamos (which would include all automobile starters and alternators). There's also NMR (MRI is merely NMR in a hospital, they took the "nuclear" out of the acronym because they knew people wouldn't go inside a big machine with the word nuclear in it). And they're very common in physics and material science research. I regularly use superconducting magnets (up to 10 Tesla) to probe nano-scale systems.

      [I'm not an EE, I'm a physics graduate student. But I did EE research (microwave and optoelectronic) with professional EE's for several years before coming to grad school.]

      --

      make world, not war

  7. From Family Guy: (obligated!) by Man+in+Spandex · · Score: 4, Funny

    Museum guy: Because you touch yourself at night!

  8. Plasma by DiracFeynman · · Score: 2, Insightful

    Plasma physicists have been saying this for a long time.

  9. Solved? by forceflow2 · · Score: 5, Insightful

    I'm confused. The title suggests they've solved the mystery, but didn't they just find a huge clue? I mean, I can't come upon a murder, find a footprint, and say I finished. There's much more to it than that. Yes, this is a huge step, but no, everything isn't "solved." In fact, they could be completely wrong...

    1. Re:Solved? by Daniel+Dvorkin · · Score: 2, Interesting
      "...all we have is theory, belief and evidence (theory and belief being differentiated only by the reliance on evidence)."

      Seems awfully like religon to me.
      Facts are what make true science, no? Perhaps you reveal that science relies on the same basis and lacking anything else to prove otherwise, becomes fact?


      Yes, actually, if you put it that way, it does make science sound something like religion ... if you ignore the "evidence" part. That's what religion invariably fails to provide. And no, someone's book of collected folktales does not constitute evidence. At most, it provides a clue as to where to look.

      GP poster unfortunately got the terms mixed up, which is where the erroneous "it's just a theory" argument gets its foot in the door. A better way to put it would be: "... all we have is hypothesis, evidence, and theory (hypothesis and theory being differentiated only by the reliance on evidence)." And "theory" in the scientific sense is what most people mean when they say "scientific fact," not "educated guess" as it is in everyday speech. (An educated guess in science is, of course, a "hypothesis.")

      This is something a lot of people seem to have trouble getting their minds around, but it's critical to an understanding of what science is. Science does not, and cannot, make a claim to Absolute Truth in the way that religion does; if it does, it's no longer science. 2+2=4 is a fact; E=mc^2 is a theory, although one that's extraordinarily well supported by the evidence, and unlikely ever to be disproven -- unlikely, not certain. Everything, including the evidence itself, is subject to revision if someone else comes along and does a better job.

      This uncertainty bothers a lot of people, which (I assume, as a nonbeliever) is why they so often seek the comfort of religious absolutes. But it is also the attitude which has produced every bit of technology, from flint spearheads to the internet, that separates us from the apes -- and that technology is what enables us to live our lives as human beings. So, judging by the evidence, it's the way to go.
      --
      The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
  10. Really? by Anonymous Coward · · Score: 5, Informative

    Whatever would iron have to do with this? This is about plasma movement in a magnetic field. Or did you think star explosions ejected nice, neutral iron atoms? Here's a clue: the magnetic moment of iron is caused by its outer electrons.

  11. Re:I figured this would happen sooner or later. by jnik · · Score: 4, Insightful

    Uh, no. The iron has nothing to do with it--or, at least very little. Ferromagnetism really has nothing to do with it. It's all about plasma effects: charged particles can't travel transverse to a strong magnetic field since the v-cross-B force bends the path--think cyclotron.

    This is a fairly nifty result--they're combining existing technique (Zeeman splitting measurements have been established for quite awhile as the means of measuring the field of sunspots) with some pretty serious equipment, and likely a lot of patience, to verify that the fields are strong enough to determine the shape of the plasma. Not a surprising result but a good piece of work just the same.

  12. On a similar note... by eMartin · · Score: 2, Interesting

    What I've always wondered is why the orbits of objects as parts of galaxies, solar systems, or even planet/moon systems pretty much share a common plane. And then, even the rotation of the bodies themselves also line up for the most part.

    Why don't they all rotate and orbit in any direction they want?

    Does gravity just even this all out over time when the objects pass near each other?

    1. Re:On a similar note... by (negative+video) · · Score: 3, Informative
      Consider a cloud that has net angular momentum. As the consitutents of the cloud collide, their random orbital motions get turned into heat. After a long time, all that's left is the average angular momentum: a bunch of objects orbiting in the same direction in the same plane.

      It doesn't turn into a single spinning ball because as the constituents collide, they sometimes stick. The more the empty spaces between them grow, the less often they collide. (Collision rate scales as the third power of the mean free path.) In a mature planetary system or galaxy, collisions between major bodies are so rare that they're nearly unheard of.

    2. Re:On a similar note... by StarsAreAlsoFire · · Score: 5, Informative

      On a solar system scale, the spin of the central body plays a large role in this, but it is still a kind of a game of chase-the-tail.

      When the whole system is still gas, something starts it spinning -- a simple thing like a star passing nearby gives objects (the gas particles) a bit of angular moment, which is thus transferred to the system as a whole over eons of time through collsions, gravity, magnetic forces, etc.

      Now, if a LARGE object passed by in the XY plane, and a SMALL object passed by in the YZ plane, you will end up with a spin *mostly* in the XY plane, but the *WHOLE SYSTEM* will balance out with a single plane of spin somewhere in between.

      Eventually the smaller objects become larger objects, which collide less, thus distributing the angular moment less efficiently. There may be one central body spinning in the XY plane, but a few of the large objects can have a wildly different orbital plane. But not many objects will HAVE this wildly different orbital plane, because back when the system was being formed, the angular moment transfer WAS very efficient.

      Also, 'circular' orbits, like the earths or mars or Jupiters, are fairly rare on a random scale of things; and if you have a bunch of objects orbiting in different planes with highly ellipical orbits, they have a much higher chance of smacking into each other (or some larger object, like jupiter) than the same object would if it were in a more circular orbit which happened to be in a different plane than that of the central masses spin. Don't forget the time scales in question here!

      Now, finally, in systems like that of the Earth and its huge moon, you get tidal interactions; while the moon will never shift in its orbit enough to be in an equatorial orbit, it *does* shift more closely to one every day, thanks to the 'gravity drag' between itself and Earth. Really what is happening is that the Earths spin is accelerated in the direction of the moons travel (really, this is slowing our spin rate down, think acceleration in the physics sense). Earth has already done this to the moon; hence the 'tidal lock' which has the moon presenting the same side to Earth at all times.

      Were you to watch the Earth moon system forever, eventually what you would see is two bodies rotating about a central point, both with the axis of spin of each body being parallel to the axis of rotation about said central point (hope you can visualise that!). In reality this won't occur in any amount of time, the influence of the sun, and the fact that the moon would actually leave earths gravitation influence before alignment could occur prevent it. (The orbit of the moon gets larger as it steals earths rotational momentum).

      That was fun.

    3. Re:On a similar note... by Aero · · Score: 2, Informative

      The Earth and its moon already do rotate about a common point -- the center-of-mass of the combined system. It's just that given the relative masses of the two bodies, the center of mass is pretty darn close to the center of mass of the Earth.

      --
      We can believe in you for 3 minutes, but beyond that, even the King of All Cosmos can't be expected to wait.
    4. Re:On a similar note... by StarsAreAlsoFire · · Score: 2, Interesting

      True enough. However, I felt the need to point out that a truly static field would not rotate as it compressed. Much like an ice-skater standing on ice with her arms out will not magically begin to spin when she pulls her arms in.

      Its just easier to visualize a rock passing by and stirring up motion than a super-nove 200K light-years away doing the same :~)

      Cheers,

  13. Solved? Yeah sure.... by helioquake · · Score: 2, Interesting

    Ask astronomers again in a couple of months if they all agree if the morphology of planetary nebulae is solved by the magnetic field alone.

    It's cool that they had done POLARIMETRIC measurement of these objects (that's far more dead than UV spectroscopy), however. Especially there is a star like Eta Carinae which seems to have a weaker magnetic field and its bi-polar structure is being driven by its stellar wind alone.

  14. Orbital planes by CryoPenguin · · Score: 4, Interesting

    (IANA astromoner, just a physicist)

    You have to consider where they got the angular momentum to begin with:
    A solar system isn't a bunch of objects that happen to be in the same place. It was originally a gas cloud (perhaps a nebula), which had a little bit of rotation (from whatever source: nova, magnetic fields, or the like). The gas particles, while very dilute from our standards, still interact enough to equalize their (average) velocities. As it collapses, conservation of angular momentum makes it spin faster, until it's dense enough for objects (asteroids, planets, sun) to condense. And since they all condensed out of that same cloud, they're all approximately aligned to the same orbital plane that the original cloud had. (The same explanation applies to why the axes of rotation are also mostly aligned.)

  15. Re:West: +1; China: 0 by Anonymous Coward · · Score: 2, Insightful

    Four words:

    Correlation.
    Is.
    Not.
    Causation.

    Have a nice day...

  16. Re:Sun like stars? by Anonymous Coward · · Score: 2, Informative

    Planetary nebulae are not formed by explosion (well, not violent explosion, anyway). And, yes our Sun will form a planetary nebula some day (billions of years from now). The Sun will eventually become a Red Giant star, true. At the end of its Red Giant phase it will shed its outer envelope, exposing its core. That core is what becomes a White Dwarf. The outer envelope becomes the nebula.

    The Sun is not and never will be a Brown Dwarf. A Brown Dwarf is a failed star wanna-be, one that almost (but not quite) started a sustainable nuclear reaction in its core. A Brown Dwarf is not really a star at all. Stars do not become Brown Dwarfs. Stars end up as either White Dwarfs, Neutron Stars, or Black Holes (or some exotic variant of one of those three).

  17. VLT Lore -- The Yellow Submarine by mindpixel · · Score: 2, Informative

    Once upon a time there was a telescope operator who was very nervous and when rain clouds threatened Paranal one night her nervousness turned to panic and she could not break from her very long closing script and just close the damn doors no matter the state of the system and hundreds of gallons of rain fell onto the eight meter collecting surface and washed through the central hole in the mirror and down filling the large yellow camera the size of four refrigerators mounted below. That instrument lovingly refered to on Cerror Paranal as The Yellow Submarine is FORS1--the one that intercepted the photons that caused you to read this today.