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Anomalous Pulsar In Binary System Stymies Theorists

Posted by kdawson on from the dizzy-making dept.

Science Daily has word of a millisecond pulsar in the wrong kind of binary system that has astronomers scratching their heads. According to current models of pulsar evolution, such a system should have no way to develop. The pulsar J1903+0327, which rotates 465 times per second, seems to be in a highly elongated orbit around a Sun-like star. Quoting: "Astronomers think most millisecond pulsars are sped up by material falling onto them from a companion star. This requires the pulsar to be in a tight orbit around its companion that becomes more and more circular with time. The orbits of some millisecond pulsars are the most perfect circles in the Universe, so the elongated orbit of the new pulsar is a mystery."

53 comments

  1. It's a signal from the Cheela by argent · · Score: 2, Interesting

    See what happens when real physicists write SF!

    1. Re:It's a signal from the Cheela by Vectronic · · Score: 3, Funny

      Write Said Fred... is a physicist?

      I'm too sexy for this comment.

  2. More than meets the eye? by ee_smajors · · Score: 2, Interesting

    Perhaps the pulsar is closely paired with another small star and the pair has just be captured by a larger star. Wonders never cease!

    1. Re:More than meets the eye? by $RANDOMLUSER · · Score: 1

      The pulsar could be paired with a black hole, or another neutron star which is not pointed our way. The visible star could have been captured by the pair, forming a triple.

      --
      No folly is more costly than the folly of intolerant idealism. - Winston Churchill
    2. Re:More than meets the eye? by Gat0r30y · · Score: 4, Informative
      The article discusses this option, and actually finds it the most satisfying explanation. -

      A third scenario says the pulsar may be part of a triple, not a double, star system. In this case, the pulsar's 95-day orbit is around a neutron star or white dwarf, not the Sun-like star seen in the infrared image. The Sun-like star would then be in a more-distant orbit around the pulsar and its close companion Most certainly a quite intriguing possibility.
      --
      Prediction: The real iPhone killer is going to be sex robots from Japan. Think about it.
  3. Perhaps by Anonymous Coward · · Score: 0

    Perhaps it's a physics experiment gone terribly wrong -- beware of the particle accelerator!

  4. LGM? by Anonymous Coward · · Score: 0

    Hey, just asking...

  5. Aha! by loftwyr · · Score: 3, Funny

    This will be the iron clad proof of Creationism! Only (insert your favourite supreme being here) could have put such an anomaly there!

    All hail (insert your favourite supreme being here)!

    1. Re:Aha! by argent · · Score: 2, Funny

      The FSM hates touching pulsars with his noodly appendage... he gets gravel-burns like you wouldn't believe.

  6. A simple answer by DaveV1.0 · · Score: 1

    The pulsar was captured by the star and is now in a elongated, possibly unstable and decaying, orbit.

    Oh, wait, that is too simple an explanation.

    --
    There is no "-1 offended" or "-1 you don't agree with me" mod options for a reason.
    1. Re:A simple answer by CheshireCatCO · · Score: 1

      How do you capture a pulsar? You have to shed energy somehow. I suppose binary capture is possible, but that seems like the only real option here.

    2. Re:A simple answer by SatanicPuppy · · Score: 1

      Not at all. If one is loose, all you need is a sufficiently massive body, and the right vector of approach. Obviously if the pulsar is moving at an extreme relative velocity, or if it is more massive than the object its passing, it is unlikely to fall into orbit.

      But anything can be pulled into a gravitational orbit if the central body is massive enough. Most pulsars aren't more than one or 2 solar masses, and stars can generally exist up to around 5 solar masses...Bigger than that, and you get a black hole.

      --
      ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
    3. Re:A simple answer by CheshireCatCO · · Score: 3, Informative

      What the heck are you talking about? If you have a positive relative energy before the encounter (which you must if you start not in orbit), you must dissipate energy in order to get captured into orbit (which requires a negative relative energy). The masses of the bodies involved do not change that simple physics.

    4. Re:A simple answer by DaveV1.0 · · Score: 1

      Well, first it could be a small pulsar and a large yellow star. And, if they have a low relative velocity, then the relative energy would be slow.

      And, the orbit may not be stable. It could be slowly collapsing.

      --
      There is no "-1 offended" or "-1 you don't agree with me" mod options for a reason.
    5. Re:A simple answer by CheshireCatCO · · Score: 2, Informative

      You miss the point. They cannot be in orbit if they started out not in orbit UNLESS there is energy lost during the capturing. This is basic physics stemming for binding energies.

      With planets, you can dissipate energy this with atmospheric drag, firing rockets (if you're a spacecraft), or three-body capture*. Only the last of these works with stars, and that's a dubious proposition since the millisecond pulsar would probably have been pretty close to its partner before the capture making it hard to strip during the encounter.

      * In the interest of honesty, tides and gravity waves might do it, too, but in practice, their timescale for action is much too long to assist a capture.

    6. Re:A simple answer by SatanicPuppy · · Score: 1

      Gravitational attraction is proportional to mass (and distance). Assuming that the pulsar is fairly typical, that means its between 1 and 2 solar masses; couple mass and velocity and you get momentum, which, unless I am mistaken, is the more common term for the energy you are talking about.

      The central body must be able to exert a force great enough to overcome the momentum of the unattached body. For it to have a chance of doing this, it must necessarily be more massive than the pulsar, probably substantially.

      Since we can't know the initial relative velocity (or even if there was one) we have to judge by the known variables; the relative masses. Is the central body massive enough to have picked up an object as heavy as a pulsar?

      It's the easiest way to determine if it is possible that the pulsar was captured, or whether it must have formed there.

      --
      ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
    7. Re:A simple answer by CheshireCatCO · · Score: 2, Insightful

      Arg, no. No, no, and no.

      Momentum is not energy. They are separate quantities and are conserved separately. The mass of the star is, as I stated earlier, irrelevant. When you have two bodies, the bind energy DOES NOT CHANGE during an interaction without some other dissipation. Gravity is a conservative force.

      Look, I appreciate that you're throwing ideas out there, but this is pretty basic physics that we have a good handle on. If you don't believe me (which is fine!), look some of this stuff up for yourself.

      Also, for the record, the star is less massive than the pulsar: the diagram of the orbits that I saw made it pretty clear that the star has the larger orbit.

    8. Re:A simple answer by SatanicPuppy · · Score: 2, Interesting

      I'm trying to figure out what other energy would apply. It's more just an honest question (my physics is obviously more of the terrestrial sort). Would something have to shed mass or slam into an orbiting body or something similar, in order to be bound?

      --
      ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
    9. Re:A simple answer by Scott+Ransom · · Score: 2, Informative

      You are correct that you need a dissipation mechanism to capture a pulsar into a new orbit.

      For this system, assuming it started out in the dense stellar environment in a globular cluster, exchange encounters between multiple stars (3 or 4, i.e. single-binary or binary-binary) can provide the dissipation since the lowest mass stars (i.e. not the pulsar) tend to get energy boosts and are then ejected from the encounter. Alternatively, as you suggest, tides during a very close encounter can lead to a capture.

      However, for this system, we have reasons for thinking that a triple system origin is a better explanation than an exchange encounter and subsequent ejection from a globular cluster (all this is described in the paper which will be available on the arXiv tomorrow night and which is on the Science website now).

      Scott

    10. Re:A simple answer by Scott+Ransom · · Score: 2, Informative

      For the triple scenario you never have to capture a pulsar. You only have to have the triple stellar system survive the supernova that created the neutron star (i.e. pulsars are neutron stars) and then subsequently, one of the other stars has to "recycle" the neutron star into a millisecond pulsar via accretion. The recycling process happens when a "normal" main-sequence star evolves into a red giant and dumps its outer envelope into a disk around a companion neutron star. When recycling is finished, you are left with a pulsar-white dwarf "binary" in a close-in orbit, and a main-sequence star orbiting both of those in a much larger orbit.

      Scott

      PS: Note that there is a another slightly different triple scenario that we mention in the paper where, continuing from above, the pulsar ablates away its white dwarf companion with a relativistic wind over a billion years or so and we are left with the pulsar main-sequence binary that we apparently see now.

    11. Re:A simple answer by CheshireCatCO · · Score: 1

      There's only one energy here. You are, I think, confusing energy with momentum. These are very different quantities.

      Look, here's the energy of two gravitationally interacting bodies:

      E = 1/2 (m1 v1^2 + m2 v2^2) - G m1 m1/r

      For gravitationally bound bodies (i.e., in orbit), E0. (E=0 basically never happens for statistical reasons.)

      Now, gravitation is a conservative force (never mind how you prove that for now), so E does not change during an interaction. v1 and v2 might increases as r decreases, by E does not change.

      So if you start unbound (E>0), you cannot get E0 unless you dissipate energy. The gravity of the two bodies cannot change their mutual binding energy, so you need some other process.

    12. Re:A simple answer by sp332 · · Score: 1, Informative

      Here, I know this is a little backward, but it's cool and it illustrates what is conserved. Try it yourself: http://isthis4real.com/orbit.xml

    13. Re:A simple answer by CheshireCatCO · · Score: 1

      Yeah, I would have thought starting it as a 3-body system would work better.

      Tides wouldn't work very well I shouldn't think. There's just not enough dissipation at the required rate I'm pretty sure.

    14. Re:A simple answer by CheshireCatCO · · Score: 1

      Gah, I missed the fact that < gets consumed by Slashdot's formatting. Everywhere that there's an "E0" in the last post, assume that it's "E<0", please. :-)

    15. Re:A simple answer by CheshireCatCO · · Score: 1

      Yeah, a triple-system definitely struck me as more likely than capture. I just didn't mention it because it wasn't what was being suggested here. :-)

    16. Re:A simple answer by DirkGently · · Score: 1

      I'm way the hell out of my league here, but the xscreensaver "attraction" does a pretty good job of showing you how orbits are attained with 3 separate masses.

      --

      I keep trying to pick fights, but I can't shake this Excellent karma.

    17. Re:A simple answer by WalksOnDirt · · Score: 1

      Would something have to shed mass or slam into an orbiting body or something similar, in order to be bound? That could work, but a more reasonable process is that a binary (or multiple) star system interacted with the pulsar system, then the excess energy could be carried away by the stars not captured. Or a single star could displace another star (or perhaps even a large planet) that was already there. In most of the galaxy it is very rare for star systems to come close enough to interact like that though. It is much more likely that the pulsar was part of a multiple star system when it formed, and the system held together through the supernova that created it.

      ***

      It should be easy to tell from doppler shift that a pulsar is in a tight binary with another star, unless the axis of the orbit points almost right at us. What's missing from the article is how closely constrained that alignment is, and therefore what the odds against it are. If the odds against that are many times the number of millisecond pulsars we've see it would make people suspect some other mechanism to create millisecond pulsars might exist.
      --
      a,e,i,o,u and sometimes w and y (at be if of up cwm by)
    18. Re:A simple answer by 0p7imu5_P2im3 · · Score: 1

      Could a supernova on entry into the yellow star's system have caused the right amount of force?

      I.e., The pulsar (and invisible twin) are traveling towards a star (or vice versa, depending on POV). It supernovas as they are passing by, slowing the twin system just enough to pick up all the debris from the newborn system in an elliptical orbit, or vice versa. The orbit is far enough away from the pulsar or newborn system so as to allow the newborn system to develop naturally into another star system. The trinary system we see now is what occurs.

      Does this make sense?

      --
      Resistance is futile. Your technological distinctiveness will be added to our own. You will become one with the morgue
    19. Re:A simple answer by CheshireCatCO · · Score: 1

      I'm not sure I followed all of that, but an SN could, I suppose, in theory provide the braking force needed to shed some of the energy. But it's extremely unlikely, the timing would have to be awfully precise.

      The triple-star system idea seems a lot more likely.

    20. Re:A simple answer by Cyberax · · Score: 1

      Maybe, it was a binary system which captured a neutron star, ejecting one companion in the process.

      It's possible, but very unlikely.

    21. Re:A simple answer by 0p7imu5_P2im3 · · Score: 1

      Yeah, I wasn't too concise with my description. Seems like you got it though.

      As to the likelihood of it happening, though, we (the human race) have seen stranger astronomic coincidents.

      --
      Resistance is futile. Your technological distinctiveness will be added to our own. You will become one with the morgue
    22. Re:A simple answer by CheshireCatCO · · Score: 1

      Not sure we've seen strange coincidences in the sky, but I'd say that we humans may be more unlikely. :-)

    23. Re:A simple answer by CheshireCatCO · · Score: 1

      Yeah, that's the three-body problem. Of all the capture scenarios, that seems the most likely. However, it still seems unlikely since a millisecond pulsar would be close to its companion and therefore hard to strip away.

    24. Re:A simple answer by Cyberax · · Score: 1

      How about a double-supernova? It can, in theory, eject a pulsar with a pretty good proper velocity.

      BTW, I'm not an astrophysicist, but right now I'm running different variants of capture scenarios on my cluster.

    25. Re:A simple answer by Anonymous Coward · · Score: 1, Informative

      Here, I know this is a little backward, but it's cool and it illustrates what is conserved. Try it yourself: http://isthis4real.com/orbit.xml

      It's also wrong. The creationist propaganda that comes with it is exactly why I get pissed off at creationists and ID people. They try to use flawed scientific arguments that sounds right to the uneducated.

      It ignores gravitational interactions with other bodies in the solar system, ignores friction with the atmosphere (although it does include some type of friction when the two bodies are actually touching one another) when you start at ground level, and it doesn't allow you to move the "outer space" starting point.

    26. Re:A simple answer by lgw · · Score: 1

      If the neutron star is passing close enough to the companion star to swallow chucks of it, there's your "other process". This is the exact mechanism by which these orbits become so circular over time. This pair of stars may simply be at the start of the process - statisticlly unlikely, but then this observation is statistically rare, so why not?

      --
      Socialism: a lie told by totalitarians and believed by fools.
    27. Re:A simple answer by Tango42 · · Score: 1

      Did you even read the summary? The same mechanism that made the pulsar rotate so fast should have circularised the orbit. Getting the pulsar into a highly eccentric orbit isn't hard, but getting it rotating that fast in one is.

    28. Re:A simple answer by CheshireCatCO · · Score: 1

      A double-super nova?

      A single SN can eject a pulsar at high speeds (this isn't even just a theory, we observe them moving pretty fast so it's a pretty reasonable conclusions :-), but remember that the pulsar started out inside the star, thus felt a lot of force. As you get farther away, the force falls off as 1/r^2 (one would think, perhaps a bit faster). At reasonable astronomical distances, it probably wouldn't be very big. Perhaps juuust enough to switch a pass into a capture, though, it it was marginal to begin with.

    29. Re:A simple answer by VernonNemitz · · Score: 1

      Considering the masses of the stars involved, I'd say that the pulsar captured one member of an approaching pair of stars, and ejected the other. However, this doesn't explain why the pulsar is flickering at a millisecond rate. A young pulsar (like the one in the Crab Nebula) can be expected to pulse that fast, but if it was young, then where is the nebula (supernova remnant expanding gas cloud)? If it is older, then it can only (so far as we know) flicker at millisecond rate by getting a boost (typically by sucking in gas from a second and very close star). Depending on how crowded the stars are in that region, we could speculate about a SMALL star that got completely sucked by the pulsar, after which the pulsar captured one of a pair...

  7. Re:i have nothing to say by Perseid · · Score: 2, Funny

    I don't think it runs Linux.

  8. Re:i have nothing to say by UID30 · · Score: 4, Funny

    I don't think it runs Linux. I dunno ... about 2/3 of the way down in the 2.6.25.4 patch notes ... yeah ... right there:

    commit f96e856cd870007bb8f344e62eff228eba3f6989
    Author: Chris Wright
    Date: Mon May 5 13:50:24 2008 -0700

            added support for elongated orbit millisecond pulsars.
    --
    "Glory is fleeting, but obscurity is forever." - Napoleon Bonaparte
  9. Problems with kernel 2.6.25.4 by Cassini2 · · Score: 3, Funny

    I don't think it runs Linux.
    I dunno ... about 2/3 of the way down in the 2.6.25.4 patch notes ... yeah ... right there:

    - added support for elongated orbit millisecond pulsars.

    I've been working on simulations of the 2.6.25.4 kernel running on neutron stars. Shortly after getting the 256-node Beowulf cluster simulation booted up, the cluster encounters severe gravitational disturbances. These interfere with network communications. I asked a physicist, and he started muttering something about event horizons and black holes. I think we are going to need a better patch.

  10. It is the mother ship calling! by slashname3 · · Score: 1

    Everyone is wrong! It is the mother ship calling! The signal has finally arrived and been detected! Everyone head to the embarkation points and prepare to depart!

    This was suppose to have back on 12/31/2000 at midnight but for some reason the signal was not detected at that time. The time is now upon us! Finally!

  11. Millisecond? by rastoboy29 · · Score: 1

    If it only rotates 465 times per second, wouldn't that just make it a "centisecond" pulsar?  Wouldn't it have to rotate at least a thousand times per second to be a millisecond?

    :-D

    --
    expandfairuse.org
    1. Re:Millisecond? by phliar · · Score: 1

      If it rotates 465 times a second, the period of its rotation is 2.15 milliseconds. I think 2.15 is closer to 1 than to 10... at least in some states!

      --
      Unlimited growth == Cancer.
  12. Yes, millisecond by Anonymous Coward · · Score: 0

    1/465 sec ~= .00215 sec ~= .002 sec
    Sot it's about 2 milliseconds, which means it's on the order of a millisecond, which means it's a millisecond class pulsar.

    And since we're picking semantic nits, another equally valid way of looking at it is to say it would have to rotate at most a thousand times a second to be a "millisecond" pulsar; otherwise it would a smaller denomination (as opposed to "otherwise it would be a larger denomination" in the case of your post).

  13. Third object? by Chris+Snook · · Score: 1

    According to accretion theory, there's no way Venus could have formed with its spin in the opposite direction of the solar system. The prevailing theory is that a protoplanet smashed into it and radically changed its spin, possibly multiple times. Same goes for Uranus, which spins sideways, rather than backwards.

    It's entirely possible that this pulsar formed in the usual way, but some interaction with a very massive object pulled it out of its pristine circular orbit. Given how these orbits stabilize themselves, it may have happened fairly recently, so there could still be some evidence nearby in the sky.

    --
    There's no failure quite as dissatisfying as a complete and total solution to the wrong problem.
  14. ...or a sign of the end! by dfedfe · · Score: 1

    Suspicious binary systems might also be a sign of bigger problems, like in Greg Egan's Diaspora (one of the coolest novels I've read in a long time). PANIC!

    1. Re:...or a sign of the end! by argent · · Score: 1

      Don't panic, start looking for anomalously heavy neutrons.

  15. Elongated Orbit Pulsars by Heather+D · · Score: 1
    There's no particular reason why a pulsar cannot 'spin up' in an elongated orbit. It would take longer though, and it would need to be timed in such a way that it's material transfer events maintain the orbit, rather than 'flattening' it out.

    Or, perhaps more likely, an especially energetic eruption pushed it out of a formerly 'flattened' orbit.