Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Could 0.9c neutron star jets originate from the core?

  1. Jan 25, 2016 #1
  2. jcsd
  3. Jan 26, 2016 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    That would require some unknown high energy reaction that is sufficient to push the matter against the gravity of the star, against the drag and weight of the outer layers, and still have enough left over so that known processes can accelerate the mass to the very high speeds mentioned.
    This is: as opposed to an unknown high energy process that only needs to accelerate the mass from close to the surface, little drag, less gravity etc to fight?

    Next step is usually Occam's Razor.
    Do you have any information besides the article in the link?
     
  4. Jan 26, 2016 #3
    “That would require some unknown high energy reaction that is sufficient to push the matter against the gravity of the star, against the drag and weight of the outer layers, and still have enough left over so that known processes can accelerate the mass to the very high speeds mentioned.”

    The simplest process I can think of would be the disintegration of a nucleus into quark and lepton particles that have a total rest mass under about 10 MeV and an original kinetic energy of about 930 MeV.

    “Do you have any information besides the article in the link?”

    No, I’m focusing on just PSR J1023+0038. With conventional explanations neutron star jets should not be >0.5c. One would think an article about a neutron star jet >0.9c would have attracted more attention. Maybe the information in the link is erroneous. That would be a bummer!

    Another factor, quoting from Wikipedia: “One of the best ways of exploring how jets are produced is to determine the composition of the jets at a radius where they can be directly observed. For example, if a jet originates in the accretion disc, its plasma is likely to have electron-ion composition, whereas if it originates in the black hole it will likely be electron-positron in nature.”

    Also if jets do not always occur simultaneously with accretion it’s a red flag about how jets are produced.
     
  5. Jan 26, 2016 #4
  6. Jan 27, 2016 #5

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    ... but it still has to get through the outer layers with enough of that energy to count ... you realize quarks don't exist by themselves. The closest you'll get is a quark-gluon plasma. So you still have trouble with Occam's razor here: why can't the jet come from the surface layers? You have the same amount of speculative hand waving and fewer obstacles.

    One of the reasons for studying these things is that they are basically a really big nucleus ... held together by gravity mostly... so here we have the intersection of a QM object with a gravitational object. The intersection of QM and gravity remains a mystery so: very interesting.

    Note: please do not use wikipedia as a starting point to formulating novel theories.
    What you are doing is basically speculation. I think there are rules about speculation around someplace.
    The short answer to your original question is "nobody knows: there is not enough information".

    5Mmph is a bit under 1% the speed of light, and 10x the speed of the Solar System. Why would travelling this fast mean it does not have a jet? Remember that all reference frames are equal, so, if it is OK for a stationary neutron star to jet, the same mechanism should work for a moving one. The article you cite does not seem to think the jet is at all unexpected.

    Note: is 5 million mph fast? Sounds fast ... but it's an inconvenient number so lets convert a bit:
    5000000mph is 1390mps, or 2360kmps, or 0.007c
    Well it's not relativistic (##\gamma = 1.00002##)

    To compare such slow objects, kmps (kilometer's per second) would normally be used.
    (If you want to explore astrophysics more, you should get used to the metric system.)

    The Solar system is travelling about 240kmps
    The escape velocity of the Milky Way is 317kmps
    The fastest star in the MIlky way, though, is doing: 1200kmps (2700000mph)
    ... so yes, that's pretty fast for a star.

    But this should also give you a feel for the kinds of numbers to expect.
     
    Last edited: Jan 27, 2016
  7. Jan 27, 2016 #6
    According to conventional understanding the jet mechanism is supposed to originate from accretion. How can this neutron star be accreting? It has no binary companion. Is an accreting cloud being dragged along with it? This high speed star has had a jet for over a thousand years. There is some stuff the neutron star is dragging along but its probably from the jet. I think the powerful jet is heating the stuff around the star.

    In other stationary neutron stars, jet heating of the accretion cloud could explain why the Eddington limit is sometimes exceeded.
     
  8. Jan 27, 2016 #7

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    You just suggested two mechanisms for the star having a jet just by considering what the stationary mechanism is.
    Remember that the speeds given in these articles are usually given with respect to the galactic center of mass ... though sometimes with respect to the Solar system. But we know the galactic center of mass is moving with respect to the center of mass of the local galactic cluster... so all neutron stars are in motion. All the ones you are thinking of as "stationary" are moving, and "dragging" an accretion disk with them - just like the Sun "drags" the Solar System with it. Maybe it has a close binary companion - too close to resolve just yet? Maybe some jets can persist for thousands of years apart from the companion?
    ... did you check to see if the radiation is consistent with an accretion mechanism?

    What I am trying to do here is get you talking in astrophysical terms ... i.e. you've been talking as if these velocities are somehow absolute. There is no such thing as an absolute velocity and I'm sure you've heard of this.

    But all you have is a load of "I don't know"s being the best answer.
    Feel free to speculate but remember: coming up with new and novel physical theories is easy - supporting them is hard.
     
  9. Jan 27, 2016 #8

    Dale

    Staff: Mentor

    Closed pending moderation.

    Edit: several more speculative posts have been removed and the thread will remain closed.
     
    Last edited: Jan 29, 2016
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Could 0.9c neutron star jets originate from the core?
Loading...