Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Space Science

How a Pulsar Gets Its Spin 63

Posted by Zonk from the how-the-pulsar-got-its-spin-back dept.
brian0918 writes "Until now, the assumption has been that the rapid spin of a pulsar comes from the spin of the original star. The problem was that this only explained the fastest observed pulsars. Now, researchers at Oak Ridge have shown that the spin of a pulsar is determined by the shock wave created when the star's massive iron core collapses. From the article: 'That shock wave is inherently unstable, and eventually becomes cigar-shaped instead of spherical. The instability creates two rotating flows — one in one direction directly below the shock wave and another, inner flow, that travels in the opposite direction and spins up the core. The asymmetrical flows establish a 'sloshing' motion that accounts for the pulsars' observed spin velocities from once every 15 to 300 milliseconds.'"
This discussion has been archived. No new comments can be posted.

How a Pulsar Gets Its Spin More

How a Pulsar Gets Its Spin

Comments Filter:
  • For each and shock that waves
    Another Pulsar gets it's spin
    So show you care and let your iron core collapse
    And help a pulsar spin tonight...

  • a-z (Score:5, Funny)

    by Anonymous Coward on Friday January 05, 2007 @05:42PM (#17481860)
    Mumble mumble... angular momentum...
    Therefore, God exists.

  • Bad reporting (Score:5, Insightful)

    by exp(pi*sqrt(163)) ( 613870 ) on Friday January 05, 2007 @05:45PM (#17481906) Journal
    From 'the first plausible explanation' to 'researchers at Oak Ridge have shown that the spin of a pulsar is determined by the shock wave created when the star's massive iron core collapses'. Shows how poor journalists give scientists a bad name by making their claims seem much stronger than they are. The press release is very careful in how it makes its statements. The /. story isn't.

    • Re: (Score:2)

      by jdigriz ( 676802 )
      Bah, unstable shockwave giving a pulsar its spin! Ridiculous! Pulsars obviously spin through Intelligent Exploding!

      • Re: (Score:3, Funny)

        by Surt ( 22457 )
        Bah, unstable shockwave giving a pulsar its spin! Ridiculous! Pulsars obviously spin through Intelligent Exploding!

        The sad thing about this argument is that it's clear in the original Aramaic that they meant Imploding.

        • Re: (Score:2, Funny)

          by Hal_Porter ( 817932 )
          The sad thing about this argument is that it's clear in the original Aramaic that they meant Imploding.

          God spoke the Queen's English, not some obscure semitic language.

    • Re: (Score:2)

      by njh ( 24312 )
      Perhaps the 10 well written stories were all passed over?
    • The slashdot story text is taken directly from the Oak Ridge article. Try again.
      • Having trouble telling the difference between:

        researchers at Oak Ridge have shown that the spin of a pulsar is determined by the shock wave

        and

        According to three-dimensional simulations...the spin of a pulsar is determined...by the shock wave created when the star's massive iron core collapses.

        ?

        There's a big difference between a tentative model suggested by a simulation that is explicitly described as 'plausible' and 'researchers have shown that...is determined'.

        Maybe you'd like to try again.

  • Pulsars as GPS (Score:5, Interesting)

    by mrcaseyj ( 902945 ) on Friday January 05, 2007 @05:48PM (#17481946)
    The most interesting application of pulsars I've heard of is using them like GPS transmitters. Since pulsars are about the most precise timing devices known, if you time the arrival of the pulse from at least four of them you can use the time differences to triangulate your position precisely anywhere in the solar system.

    • Re: (Score:2)

      by ArcherB ( 796902 ) *
      The most interesting application of pulsars I've heard of is using them like GPS transmitters. Since pulsars are about the most precise timing devices known, if you time the arrival of the pulse from at least four of them you can use the time differences to triangulate your position precisely anywhere in the solar system.

      You'd need a GPS device that could detect the pulses from at least two pulsars from anywhere on earth. Now if you were to create a UPS (Unversal Positioning System) device that would work

      • Re:Pulsars as GPS (Score:5, Insightful)

        by mrcaseyj ( 902945 ) on Friday January 05, 2007 @06:54PM (#17482798)
        I think the idea of Pulsar GPS is primarily intended for interplanetary spacecraft. For terrestrial stuff GPS probably works better. One problem with Pulsars is that you would have to know which pulse to measure the time difference relative to the other Pulsars. if a pulsar pulses every 300ms then the pulses will be about a third of a light second apart or about 100km. If you go 100km relative to the pulsar you might get mixed up as to which pulse to lock onto and think you hadn't moved. The problem gets worse as the pulse rate gets higher. GPS doesn't have this problem because the absolute time is encoded within the signal from each satellite so you know the date and time each pulse left the GPS satellite.

        One way to deal with the problem is to carefully keep continuous track of your position so you can keep straight which pulse to measure. If you can figure out where you are accurately enough by some other means you can figure out which pulse to measure. You can decrease the uncertainty of which pulse to use by using more than four pulsars. For example if one pulsar pulses every 7ms and another pulses every 11ms you can increase your window to 77ms by watching as they go into and out of sync.

        I'm guessing that another problem is that the pulsars probably have a rather faint signal. You may have to have four or more large high gain dish antennas pointed in different directions to pick up the signals. This would be impractical on earth for most applications and would be a lot of extra weight for a spacecraft also. You might be able to have just one dish and point it at each pulsar in turn.

        I don't see anything about this on Wikipedia. I think I'll add it one of these days.

        • Keeping exact track is not always necessary as each and every star, pulsar, etc. which emits radiation is not exactly the same as any other. With advances in sensor technology and computational abilities it is likely we will be able to know what a given pulsar by name/designation puts out, look for signatures of the closest ones and identify against the catalog, then relate their positions as seen from Earth at the time of cataloging versus what we see now, etc...

          Of course we can do this with stars as well.
          • Rather insightful idea, but if we're gonna have manned/unmanned beacons anyway, why not just use them to triangulate position?

        • Re: (Score:3, Insightful)

          by iluvcapra ( 782887 )

          a third of a light second apart or about 100km

          I think you mean 100,000 km [google.com].

          If you go 100km relative to the pulsar you might get mixed up as to which pulse to lock onto and think you hadn't moved.

          You wouldn't use the phase of the pulsar signal to get a distance reading, but you could use it's frequency as a way of identifying it uniquely, and then you would triangulate your position by getting a bearing on three or four pulsars; this is essentially how the starburst pattern on the Mariner Plaque is suppose

          • a third of a light second apart or about 100km

            I think you mean 100,000 km

            Oops.

            Ah, whats a few zeros here and there? :)

            I was writing in a hurry and the value wasn't very important anyway.

            You wouldn't use the phase of the pulsar signal to get a distance reading, but you could use it's frequency as a way of identifying it uniquely, and then you would triangulate your position by getting a bearing on three or four pulsars; this is essentially how the starburst pattern on the Mariner Plaque is supposed to work for aliens trying to find Earth. It gives the frequency of pulsars near the earth and their bearing to Sol relative to the galactic center. The aliens would identify the pulsars by their frequency, and then use their knowledge of the pulsars' absolute locations to work backward and triangulate the position of Sol (assuming these aliens, a million years from now, are able to backtrack the locations of all the pulsars, as they will all have moved relative to Sol and will have slowed down in their spinning, causing an error in our reported frequencies).

            Interesting point. The pulsars will move and slow down by the time Mariner gets anywhere (or is it Pioneer or Voyager).

            However pulsar GPS and the Pioneer plaque are both interesting and clever tricks with pulsars, but the two methods have a totally different purpose and procedure. The Pioneer plaque just uses the time between pulses to tell aliens which pulsar we are giving the distan

            • With pulsar GPS you're using changes in the arrival times of the pulses to determine if you're getting closer to the pulsar or getting farther away

              Exactly. Pulsars are like VORs but without the magnetic-north synchronization signal. You can figure your velocity to or from by measuring the doppler, but you can't figure your bearing, and therefore, cannot figure your position.

              By comparing the difference between your observation of a pulsars frequency and its frequency from a known reference, you can figure

        • Re: (Score:2)

          by vmcto ( 833771 ) *
          umm... p

          Plus there's that whole problem of the planet moving through space...
        • If every pulsar has a distinct period, how could you ever get confused which is which? Couldn't you always be able to determine this based on their periods? /forgive me if i'm missing something fundamental. it's fri night and i'm a bit lit
        • Allow me to clarify some things. I've done research in this area, and here is how a pulsar based interplanetary navigation would work.

          First, it would not use radio pulsars, because it's ridiculous to have four high gain antennas on a space craft. Rather, it would use the x-ray portion of the spectrum. X-ray detectors don't even require optics. However, with a coded aperture mask and some software, the position of the source the pulse is coming from can be determined.

          Second, you are on the right trac

          • > Second, you are on the right track with the knowing your existing position.
            > Pulsar navigation can only work with differential positions. Essentially, it
            > would provide a correction the existing intertial guidance systems.

            It would be closer to LORAN than to GPS.

    • Re:Pulsars as GPS (Score:4, Informative)

      by swebster ( 530246 ) on Friday January 05, 2007 @06:03PM (#17482192) Homepage
      This idea was used on the Pioneer plaque (http://en.wikipedia.org/wiki/Pioneer_plaque [wikipedia.org]).

    • Re: (Score:2, Interesting)

      by lowen ( 10529 )
      Being that we do pulsar research here at PARI, I'll comment on this timing thing. Some pulsars are quite regular; most however do have what are known as 'glitches' and in the case of the Crab pulsar 'giant pulses'; both of these phenomena are unpredictable and skew any timing you might receive from the pulsar. Also, pulsar timing requires some fairly extensive integration of the incoming pulses, as most pulsars miss 'beats' frequently, and pulses vary somewhat in terms of amplitude. Some pulsars exhibit
  • ...I see ALOT of things spinning when I get sloshed.

  • wait a minute. (Score:5, Funny)

    by User 956 ( 568564 ) on Friday January 05, 2007 @05:56PM (#17482078) Homepage
    Now, researchers at Oak Ridge have shown that the spin of a pulsar is determined by the shock wave created when the star's massive iron core collapses. From the article: 'That shock wave is inherently unstable, and eventually becomes cigar-shaped instead of spherical. The instability creates two rotating flows -- one in one direction directly below the shock wave and another, inner flow, that travels in the opposite direction and spins up the core. The asymmetrical flows establish a 'sloshing' motion that accounts for the pulsars' observed spin velocities from once every 15 to 300 milliseconds.'

    Hey now, it's not an asymmetrical flow that establishes an observed spin velocity. It's 'Intelligent Exploding'.

  • now I can sleep... (Score:1, Redundant)

    by mtec ( 572168 )
    ..zzzzzzzz..

  • Strange summary... (Score:4, Informative)

    by imsabbel ( 611519 ) on Friday January 05, 2007 @05:57PM (#17482092)
    The current theories also explain the slow pulsars.
    By the simple way of energy loss.
    Take the crab nebular pulsar as example. Currently spinning about 30 times per second, it will be down to 20 in a few thousand years. Those thing have huge magnetic fields, and they can couple out energy amounts into the planetary nebular even OB stars usually can only dream of.

    So no, its not like everybody was totally stupid before this theory.

    • Re: (Score:3, Funny)

      by Gospodin ( 547743 )
      ...even OB stars usually can only dream of.

      Do pulsars dream of magnetic sheep?

    • Re: (Score:2)

      by forand ( 530402 )
      Of course people were/are not stupid. However your explanation is not correct, while you can measure the spin down rate of a pulsar and correlate it with its energy loss thus giving you a good idea how the spin down evolves with time, you can also measure WHEN the neutron star was created by observing the super nova remnant or looking in history to find some observation of the event, this gives you a starting date. Before this explanation you could not have spun down the neutron star in the alotted time v

      • Re: (Score:3, Insightful)

        by iamlucky13 ( 795185 )

        Thanks for explaining that.

        However, the submission and the article are still a little strange in their word choices (mostly the submission...If you re-read the article a few times, it makes more sense). They seem to suggest that the assymetric shockwave gives the pulsars their sping, when according to the theory, it actually takes away spin. I clicked on the article wondering how in the world they were postulating massive, exploding objects with very low or possibly non-existant angular momentums.

        If I'm

  • Pulsars get sloshed every 15 to 300 milliseconds? (Score:4, Funny)

    by Picass0 ( 147474 ) on Friday January 05, 2007 @06:07PM (#17482246) Homepage Journal
    Sounds like that's where the party is at.
  • My pulsar doesn't spin like that.
  • her liberal upbrining in San Francisco politics.

  • From Kipling's "Just-so Stories" (Score:3, Funny)

    by sehlat ( 180760 ) on Friday January 05, 2007 @06:31PM (#17482572)
    "How the Pulsar Got Its Spin"

    In the galaxy, once upon a time, O my Best Beloved, there was a
    star, and it gave off light and a stellar wind. It fused hydrogen
    to helium, and developed turblence and spots, and slowly grew old,
    turning to burning helium, then heavier and really truly heavier
    elements, until it grew a Great Iron Core. ...
  • Copernicus Rove?

    He's the lesser-known twin.
  • How a pulsar gets its spin?

    ... from the Bush administration [slate.com] ?

  • Isn't that pretty much the same process by which Stella Got her Groove Back?

  • EVERYONE knows how a pulsar get's spun...

    Fox News!

  • The Universes Disco balls.
    (take a look at Orion's Travolta move if you don't believe me)
  • Subject says it all. What else but the angular momentum of the original star determines the pulsar's rotation rate? The supernova process can only determine how that angular momentum is divided between the pulsar and the ejected mass. So does this new mechanism cause mass to be ejected off-center? The news release doesn't say much, unfortunately.
  • It's spinning because gravity rules, man! That's what they taught us in astrophysics class, or PE or something ... that even though plasma fills all of space and it consists of charged particles, it doesn't actually *do* anything. It *can't* be true that those charged particles in plasma might interact with one another en masse as plasma does in order to move charged particles through fields or voltage differentials in space, or that diffuse flows of energy might exist within the universe. There's no way

  • Spindowns (Score:2, Interesting)

    by Shitok ( 1048216 )
    I think the story ought to acknowledge the larger effect which comes from the stars initial angular momentum.

    Our Sun (for example) rotates at the rate of around once per 25 days and has a radius of around 1 million km. If
    it was to collapse into a neutron star without losing any mass the moment of inertia would go down by a factor
    of (1,000,000 km/10 km)^2 = 10 billion. So the rotation rate would go up to 4500 times per second. The principle
    is the same one that makes figure skaters spin-up when they bring the

Slashdot Top Deals

Avoid strange women and temporary variables.

Close