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

State of Pulsar Theory & Observations

  1. May 7, 2010 #1
    It is interesting to compare pulsars to quasars. If one assumes the massive compact object at the center of a quasar is a physical object that has properties, is it similar to what creates the pulsar and magstar observations? What are the pulsar and magstar observations? What are the quasar observations? There do appear to be similarities.

    The pulsar observations, the quasar observations, and magstar observations are different from what one might assume based on the cartoon pictures in text books. The explanation of these differences is included in recently published papers.

    This paper was included as recommended reading at a presentation made at a pulsar conference for specialists in that field.

    F. C. Michel alleges that due to more sophisticated earth and space based telescopes there is now sufficient observational evidence to make progress in pulsar theory. Michel alleges in this paper that one obstacle to advancement in pulsar astrophysics is that specific theoretical models when they are included in text books and taught fix the thinking concerning this subject. Michel alleges that observational evidence and holistic critical fundamental physical analysis of the text book models in question shows that they are fundamentally incorrect.

    Michel's point is there was no rational reason to present the pulsar textbook model as the correct model. The class of pulsar model that he alleges may lead to a solution was postulated in the 1960s.

    http://arxiv.org/PS_cache/astro-ph/pdf/0308/0308347v1.pdf


     
  2. jcsd
  3. May 7, 2010 #2
    They are both compact objects so yes there are similarities. Black holes are actually much simplier because there is no surface to attach anything to.

    A magnetar is just a pulsar with a strong magnetic field. Quasars are likely to be massive black holes. Also, I did a literature search and it seems that people agree with Michel that the basic model of pulsars that you see in intro astronomy textbooks, just doesn't work, and people are trying to figure out what does.

    We basically do not understand how plasmas behave in high magnetic field situations.

    OK, now what? :-) :-)

    Here is a more recent paper on what we don't understand.....

    http://arxiv.org/PS_cache/arxiv/pdf/0902/0902.3821v1.pdf
     
  4. May 7, 2010 #3
    This is an interesting paper, because it has the signs of a crank paper, but it turns out that it isn't. What I did to see if it was a crank paper was to look at more recent papers and textbooks on pulsar magnetospheres, and I found a textbook which describes the basic textbook model with the warning that the model is likely to be very wrong with a reference to Michel's papers.
     
  5. May 7, 2010 #4
    Hi 2α – quant,

    I believe your comment concerning Michel is correct. I am interested in Michel’s model's charge separation. I will see if I can find any review papers that summarize that model and its competition.

    This is another review paper on pulsars and neutron stars.

    This paper notes the observations of very recent supernova collapses found the object formed has not a pulsar. That observation could mean the collapse can create a neutron star that does not have a magnetic field, the neutron magnetic field develops later, or that the collapse formed a traditional BH. If Schild's ECO assertion is correct, (See Schild thread. Schild and others allege that they have observational evidence that shows traditional BH does not exist) traditional black holes do not form. If I understand the line of thought in Schild’s paper, all neutron stars would have a magnetic field however the magnetic field would develop later as the object cooled to arrest the collapse.


    http://arxiv.org/PS_cache/astro-ph/pdf/0208/0208356v1.pdf

    http://www.chjaa.org/2008/Italy2008/P24_250_kundt_213-218.pdf

     
    Last edited by a moderator: Apr 25, 2017
  6. May 7, 2010 #5
    This is another thing is very poorly understood. We don't really have any idea what the relationship is between a progenitor star and what it leaves behind. It may be that magnetic fields and plasma play a critical role in supernova, or not.

    One thing that is helping things a lot is that we can throw more computer cycles at the problem and see what's going on.

    The people that know GR think that Schild and Mitra are cranks, and based on what I know about plasma gas dynamics, I tend to agree with the people that think they are cranks.

    Also it's very hard for a compact rotating object not to have a magnetic field, and once you have a magnetic field all sorts of wild and crazy things start to happen. The think about GR and black holes, is that if you have enough gravity, then the physics actually becomes a lot simpler because gravity overwhelms everything. Astrophysically speaking, black holes are a lot, lot more simple than neutron stars.

    One other thing is that there are a lot of professional cranks out there. Every theoretician has this wacky idea that they have about the universe, but the hard part is to keep the "inner crank" under control. (I have some *really* wacky ideas. What keeps me looking sane is that I realize how wacky my wacky ideas are.)
     
  7. May 7, 2010 #6
    Name calling seems to me to be irrational. There is no logic associate with it.

    Schild, Stanley Robertson and Darryl Leiter are quasar specialists that have multiple papers published with observational evidence that supports their assertion that there is a strong magnetic field associated with the massive objects that are believed to be in the center of most galaxies.

    http://iopscience.iop.org/1538-3881/132/1/420

    http://www.springerlink.com/content/l567753822878251/

    http://iopscience.iop.org/1538-4357/596/2/L203/pdf/17685.web.pdf

    I do not understand the emotion that appears to be attached to this subject and I do not know what to say in response to it. The objective is to solve a scientific problem. The observations do not support the classical BH model.

    As noted above there is no explanation as to what is creating the massive magnetic field in neutron stars to create the pulsar and magnetar observations yet for some reason people are convinced that it is not possible that a more massive object could have a massive magnetic field. Quite obviously if charge separates in the massive object it will not collapse. The ratio of gravitational force to electrostatic force is roughly 10^36.

    What happens in the very, very, massive object requires a complete understanding of extreme physics. The simplistic calculations that were done at the turn of the century are not applicable and appear to be some sort of weird barrier to thinking about the real world observations. The pulsar and magnetar observations are indications of what to expect at those very extreme conditions. There is a equal portion of energy in the allowed states of the massive object that arrests the collapse. In addition it is observed that the pulsar and magnetar evolve. They do not remain the same. The quasar's massive object also changes over time based on observations. That is what one would expect if the very, very, massive object is a physical object.
     
    Last edited: May 7, 2010
  8. May 8, 2010 #7
    It's not. Name calling based on fact is not irrational. There *is* logic associated with the name calling.

    Which doesn't surprise anyone. Everyone knows that there are strong magnetic fields associated with massive objects in the center of quasars, and Kip Throne showed a few years back, how you can model strong magnetic fields associated with black holes. Having strong magnetic fields gives you no problems with black holes. Now showing that you have a strong magentic field that isn't aligned the axis of rotation would be interesting.......

    Also the fact that they have multiple papers published means that they aren't totally cranks, but some of the papers published in ApJ are pretty crankish. The good/bad thing about astrophysics is that it's not hard to publish a paper, and people will tend to publish even if they think you are nuts. Also, there are distinguished professors that have ideas that everyone else thinks are nuts. Most of the time it turns out they are nuts. Sometimes they aren't.

    Science is not about resumes and awards. I know of Nobel prize winners in physics that have some really, really nutty ideas. I know of at least one Nobel prize winner that believes left and right, up and down, that black holes do not exist. I think he is wrong and nutty about this. Also crankishness and nuttiness goes with the territory. I have two or three nutty ideas of my own.

    But in any case, it's really important to understand why people think that Schild is nuts and Michel is not. There are reasons. What it boils down to is that when Michel shows his equations, people look at them at say. Yes, I see how this works. When Schild and Mitra shows his equations, people look at the equations and say "no it doesn't work that way."

    So they claim. Most people in the field strongly disagree. People are human and if someone doesn't appear to be listening to you when you state an obvious fact, the human tendency is to start talking louder.

    Ummmm... There is a quite good explanation of what causes magnetic fields in compact objects. You have a charged gas. Things are rotating quite rapidly, this creates a magnetic field. Now figuring at there is a magnetic field and the rough strength of the magnetic field is pretty easy. Figuring out the shape of the magnetic field is extremely, extremely difficult.

    Michel's papers have nothing to do with Schild, because Michel is arguing that the details of how the field is created is wrong, but with massive compact objects, it's hard not to have a magnetic field.

    Incorrect. The thing about electromagnetic fields is that the are both attractive and repulsive so at long distances the charges cancel out. Gravity is only attractive, so it wins. Any time you have a strong electromagnetic field it attracts the opposite charge so that it tends to cancel out. Note also that for these objects we are talking about magnetic fields and not static fields. Static fields don't last very long in astrophysics because you can't get large charge separations at large distances. Magentic fields last a lot longer because if you objects don't go in the direction of the charge.

    It doesn't. What you can do is to set limits. X is unknown, how much can X change things. To get an example, I don't know whether it will rain or shine tomorrow, but I do know that it won't be -100 celsius or +350 celsius. I don't know whether I will need a sweater or a rain coat, but I do know that I won't need oxygen tanks or kelvar suits. Then you ask yourself, well. if I don't know what the weather is tomorrow, how do I know that I won't need an oxygen tank, and it turns out that there are some simple equations that illustrate why you don't.

    We don't understand the details of nuclear physics at high densities. So what you do is to say, OK we don't know, so lets put in a factor in our equations that describes what we don't know. It turns out that for no set of equations of state can you avoid black holes, unless you are willing to destroy special relativity.

    You don't understand everything. You'll never understand everything. But you don't have to understand everything to understand something.

    Yes they are. You want simple calculations if they work.

    [QUOTE[The pulsar and magnetar observations are indications of what to expect at those very extreme conditions. There is a equal portion of energy in the allowed states of the massive object that arrests the collapse.[/QUOTE]

    Which falls apart once you have enough mass. The idea is pretty simple. You can't push things faster than the speed of light. Once something goes close to the speed of light, and you push on it, there isn't enough time for the material to push back, and so you lose pressure support. Electrons are light so it doesn't take much mass for them to start moving at the speed of light. Once they start moving near the speed of light, they lose pressure, and things combine to form neutrons. Once neutrons start moving near the speed of light, they lose pressure, and things collapse. If you add enough mass, anything moves near the speed of light, and you lose pressure.

    Here is another way of thinking about it. As things move close to the speed of light, they start acting like light, and you can't build a floor out of light.

    Read....

    http://en.wikipedia.org/wiki/Membrane_paradigm

    What Kip Throne has done is to take the equations of GR and they show that black holes can be thought of as physical objects even though they aren't. It turns out that as a black hole forms, it starts behaving as if it has a surface at the event horizon.

    Also people do change their minds. There was one physicist that I know of that wrote a major paper on the anthropic principle which I thought was totally insane when I first read it, but after some time I've changed my mind. But right now there are some really good reasons why people think that Schild and Mitra have their physics wrong, and it's a good idea to keep the discussion in physics rather than sociology.

    You seem to be pretty curious, and if you are at least interested in knowing in detail why I and pretty much everyone else thinks that Schild and Mitra are nuts, then I'll be happy to explain. You might end up thinking that I'm crazy and that's fine, but one point that I really want to make is that I'm not bashing Schild and Mitra because they are "different". I'm bashing them because I think they are wrong. Michel is different, but what he says makes sense to me. If you want to know why I think that Schild and Mitra are wrong, go ahead and ask.
     
  9. May 8, 2010 #8
    One big problem here is that ultimately the only way of resolving this sorts of questions is to "do the math." People come up with all sorts of rough rules intended to figure out what is going on without doing the math, but those rules tend to break down.

    I don't think I can (or should) be able to convince you that Schild and Mitra are wrong without going into the details of the the math. What I think I can convince you of is that there are good reasons to think that they are very wrong, and people aren't negative about them because they are different or original.

    We are talking about people that deal with nutty and crazy ideas like dark matter and dark energy. If you can argue that black holes don't exist and have convincing reasons behind them, that's great. The problem is that Schild and Mitra have arguments that most people including myself think are pretty fatally flawed.

    Also one thing about physics is that people can be total cranks in one field and then be totally brilliant in another. It has to do with the fact that you need to be a little crazy to come up with original ideas. Also, sometimes it's just a matter of luck. You come up with this cool idea, except that it turns out that the universe just doesn't work that way. Bummer.

    The Nobel prize winner that I knew of that was convinced up and down that black holes didn't exist, wasn't an astrophysicist, and was totally incredibly brilliant in his field. It's just that when the topic of black holes came up, people were quick to change the topic. So someone that is an expert in quasar observations could know absolutely nothing about the theoretical physics of compact objects.

    The other thing that makes the internet useful is that you don't know who you are talking do. I might have credentials that are a hundred times more impressive than someone elses, or not..... You don't know and I think it's a good thing you don't know.
     
  10. May 8, 2010 #9
    My general reaction is that all Schild and Mitra have done is to rediscover the membrane paradigm which Kip Thorne figured out in 1978. They are going through exactly the same equations and the same arguments, but I think they are just interpreting them incorrectly.

    Kip Thorne was able to show that from a distant observer, a black hole looks exactly like what Schild is describing as a MECO. From an infinite observation, you never quite see anything falling into the black hole because as things get closer to the black hole, the light rays get stretched out, and so it appears as if nothing falls into the black hole, and if you do your equations using the coordinate system of a distant observer, you get as far as I can tell the same equations as Schild and Mitra do.

    The thing about this is that this is an "optical illusion". The matter does fall into the black hole in finite time, it's just from the point of view of someone on the outside the information that matter falling into the black hole takes an infinite time to enter the black hole.

    Kip Throne's papers are really, really important because, they gave "mere mortals" like myself a way of thinking about black holes without being math supergeniuses. You think of a black hole as a membrane that has a certain charge. Once you spin that charged membrane, you get a magnetic field.

    There is a great non-technical article about the membrane paradigm in "The membrane paradigm for black holes". Scientific American 4/1988.

    The thing that I find curious is that Schild and friends don't cite any papers about the membrane paradigm even though it's pretty standard in astrophysical research.
     
  11. May 8, 2010 #10
    Also, reading over Schild's papers, I think there is some useful content in there, and if I were a peer reviewer, I would have argued that they be published. His ideas on black holes are I think nutty, but he wrote the paper carefully enough so that you don't have to accept his nutty ideas in order to agree with the point he is making in the paper.

    The other thing is that we have to be careful about what Schild thinks. It's not at all obvious from his peer-reviewed papers that he has written that he thinks black holes don't exist. He might not, but you don't have to accept any of his ideas on black holes for that paper to be useful, and since it's not clear from his papers that he thinks black holes don't exist, I don't want to have him screaming at me if it turns out that this isn't his view.

    Also it's really important to keep the ideas separate from the person or the topic under discussion.

    The other thing is that my thinking on this is very highly influenced by the fact that I do computer simulations of supernovas. One thing that you can do is to run the simulation under general relativity and then let things fall into the neutron star, and then watch a black hole form.

    The thing is that you never actually see the black hole form. What happens is that you get something that looks like a MECO. But it's not. What's happen is that you've set up the formula so that you never do see the black hole form, because you are researching supernova and not black holes.

    What happens is that as gravity increases, you set up the simulation so that part of the simulation runs slower and slower. When it becomes a black hole, the speed of the simulation is zero, and so you (intentionally) never reach a point where you see the black hole form. The outer parts of the simulation runs at "normal" speed, but the inner parts of the simulation run at "slow motion" and at the point where the black hole forms, it's "zero motion". It turns out that if you do this carefully, you end up with exactly the right results for everything outside of the black hole (and the stuff inside you don't care about).

    But the important this is that I've set up the equations to do this intentionally (see Van Riper 1979), and Kip Throne also sets of the equations to do this intentionally. What I think Schild is doing is that he is also setting up his equations to give the same result, but he may be doing this unintentionally and totally messing up the interpretation (or maybe not).

    So what this means is that Schild has a publishable paper because he gets the right results from the wrong model. That happens a lot. Newtonian mechanics is strictly speaking "wrong" but you end up with the right results.
     
  12. May 8, 2010 #11
    Schild has found evidence that there is an extremely strong magnetic field in a region of the quasar (in the core above the poles of the massive object) where an accretion disk cannot create a magnetic field (strong or weak.)

    As I noted the forbidden line emission in quasars requires the excitation of a very strong vacuum. The accretion disk is in a region surrounded by gas. The accretion disk's magnetic field therefore cannot excite a very strong vacuum. The region of the quasar above its poles has a very strong vacuum. Schild's mechanism has a massive magnetic field that is attached or is intrinsically part of the massive object, just like what we observe with a pulsar or a magnetar. The quasar's core rotates which causes the massive magnetic field to also rotate.

    Schild is not stating that an accretion disc does not get hot and likely does have a weak magnetic field associated with it. Schild's observations support the assertion that quasars can have up to two magnetic fields generated by different mechanism in different regions.

    Quasar radiate that do not have accretion disks. How is that possible if the quasar core is a classical BH?

    10% of quasars are naked quasars that do not have broad line region emissions. The BLR are thought to have been caused by the accretion disk (i.e. The accretion disc gets hot and rotates rapidly around the massive object which explains the BLR emissions.). The naked quasar's massive objects appear to not have accretion disks as they do not exhibit BLR emissions, yet they radiate. An extremely strong magnetic field anchored to a massive object will radiate. The observational evidence supports the assertion that the massive object has an intrinsic massive magnetic field.

    You say extreme physics is not relevant then you precede to tell me what happens when a massive object collapses in a very confident tone. You state that the object becomes a neutron star. Really and you know that because you read it in a text book. Is there observation evidence to support that assertion? This is not religion where the words in the books are dogma, inspired with deep meaning. The fact that you use the word "crank" makes it appear that you have decided without knowledge of the quasars observations.

    Mathematical analysis is only as good as the model and the model's assumptions. Physical observations prove or disprove the validity of the assumptions and the model. That is the scientific process.

    The observations concerning Magnetar and pulsars are relevant as the collapsing massive object produces a massive magnetic field. How? Or looking at the physical observations from another perspective why? The massive object produces a massive magnetic field to arrest the collapse. (See above for the observation that newly formed neutron stars are not pulsars. The object's magnetic field strengthens as the object cools.)

    Mitra notes that a massive magnetic field produces electron positron pairs in space. The electron positron pairs recombine producing gamma radiation. The gamma radiation arrests the collapse of the object.

    Observations indicate the massive object at the center of galaxies does not exceed 10^10 solar masses for any AGN or quasar. Why? Or asking the question another how can the massive object stop the infall. (The point is mass continues to infall in to the massive object. Dark matter if it exists make the problem more difficult to explain.) There are quasars at Z=5 whose cores are a billion solar masses. Galaxies continue (from the time of z=5 to the present) to merge, gas continues to infall in the quasars. Why do the quasars not increase in mass?

    The quasars pulsate with an increasing magnitude pulse (I will provide a link to Hawkins' papers and will explain his observations). The massive object in the center of the galaxies or in quasars is not stable. It changes overtime based on observations.
     
    Last edited: May 8, 2010
  13. May 8, 2010 #12
    I must be missing something. I see 42 published papers referenced in this paper that provides detail observational data to support the assertion that the massive object at the center of quasars and AGN has an intrinsic magnetic field. That mechanism is called a MECO. The authors are quasar specialists and senior astronomers/astrophysicists. The MECO mechanism explains other quasar mysterious such as the forbidden band emissions or why 10% of the observed quasars can radiate yet appear to not have an accretion disk.

    I must be missing something. I do not see any papers disputing the author’s findings. The authors explain how the massive object arrests its collapse through Compton photon pressure where the photons are created by electron positron pair recombination. (The electron positron pairs are created by the massive magnetic field.)

    There appears to be other observation evidence such as the pulsars and magnetar observations that supports the assertion that massive objects develop massive intrinsic magnetic fields. (I would assume also to arrest the collapse of the massive object.)

    This seems to be an open and shut case.

    Comments:
    Other quasar observations such as the forbidden region emission supports the authors assertion that quasars can have up to two magnetic fields. For example, the forbidden band emission requires the excitation of ions in a very hard vacuum. There was no explanation as to how ions could be excited by the accretion disk’s magnetic field as that region is surround by dust and gas as evidence by the absorption lines. The region above the poles of the quasar is exited by the MECO’s magnetic field. That region is separated from the accretion disk and has extremely rarefied gas.

    http://iopscience.iop.org/1538-3881/135/3/947/aj_135_3_947.text.html




     
  14. May 8, 2010 #13
    It's not from the accretion disk. It's from the black hole.

    Which as far as I can tell is exactly the dynamo mechanism that Kip Throne proposed for black holes in 1978. What Throne was able to show was that general relativity causes a black hole to behave as if it were a conductivity sphere. Once you rotate the sphere you get a dynamo effect that can cause the black hole to have a strong magnetic field.

    Now it could be that Schild thinks that there is something wrong with that mechanism, but since he hasn't referenced it in any paper that I've seen, I can't tell.

    Which is not inconsistent with a black hole.

    Yes, and you only have a problem if you assert that black holes can't have intrinsic magnetic fields. They can.

    No. It's because no one has detected any pulsars more than 1.7 solar masses, and all the known compact objects greater than 3 solar masses don't show any bursting behavior.

    You can have a black hole with a strong magnetic field, but because the field is disconnected with anything that is happening inside the black hole, you end don't end up with sudden bursts or pulsations which you do with pulsars.

    Now if you show me a 4 solar mass pulsar, that changes everything. What you have shown me is a ultra massive object with a strong magnetic field. Unless you can show that you can't get a strong magnetic field from a black hole, that's irrelevent.

    OK. this is a different mechanism from the anything that you've described in any papers that you have cited. I can't comment on this since I haven't seen the math for this. If you are trying to argue that a spinning object produces a magnetic field that produces an explosion (i.e. a supernova), then this is something that people I know have been working on, but it's a different mechanism than the one that any paper you've cited has presented.

    Again, this is a different mechanism than any thing that you've presented. I can't comment on how this will or won't work because I haven't seen the math. One problem that I see with this mechanism is that in collapsing neutron stars, the main energy losses are from neutrinos, and that's what kills pressure support.

    It doesn't, you have a black hole that keeps gobbling stuff up until it runs out of gas to gobble up.
     
  15. May 8, 2010 #14
    Yes. What you are missing is that somehow you seem to have this notion that black holes can't have intrinsic magnetic fields when in fact Kip Thorne has shown that they can.

    https://www.amazon.com/Black-Holes-Membrane-Kip-Thorne/dp/0300037708

    Now the magnetic field around black holes are quite different from the magnetic field around neutron stars, which nicely explains why 1.2 solar mass compact objects behave differently than 8 solar mass compact objects.

    Otherwise known as a black hole. Black holes can have intrinsic magnetic fields. The reason that Schild is able to publish even though he has some weird ideas about black holes is that when anyone reads the word MECO, they just replace it with "black hole."

    You don't see any papers disputing the author's findings that there is a massive object in the middle of a quasar with a massive magnetic field that producing the various observations that we see. It's just that pretty much everyone thinks that it's a black hole. Now as far as the idea that black holes don't exist, you'll note that in none of the published papers do they very loudly make the claim that what is producing the radiation is not a black hole.

    One point here. It's OK to be nutty. Sometimes cranks and nutcases turn out to be right (continental drift for example). It's not OK to argue that the scientific consensus supports you when it doesn't. If you think that everyone is wrong, that's fine. If tomorrow, someone points out a 4 solar mass pulsar, then at that point Mitra is a genius. If not, then not.

    Not in any of the papers you've cited. If you have some other papers that describe this mechanism, I'd like to see them.

    The problem that you have is that the main energy losses are neutrino losses. You can increase the photon pressure all you want, it's not going to change anything. Also if you increase pressure due to photons, then you decrease magnetic pressure.

    The other thing is that if you increase the mass of the collapsing object, then eventually gravity wins.

    Absolutely!!!

    Maybe. I actually know some colleagues of mine that are working to see if you can have massive magnetic fields stop the collapse of a massive star. and produce a supernova. I also happen to be friends with the guy that invented the idea of the magnetar.

    It's not. One big problem with magnetic field is that magnetism doesn't push in the direction of the magnetic field. This means that you could have a huge magnetic field, but it just causes the object to spin faster and faster. The other problem is that if you have enough mass, gravity wins. Magnetism is energy and if you require a strong magnetic field to halt the collapse, E=mc^2 and that magnetic field creates a gravitational field that causes the collapse to accelerate.

    It's *really* hard to do these calculations because there are so many thing going on. One problem that we have is that if you put all of the physics into a computer, and just let it run, what ends to happen is that everything ends up collapsing into a black hole, even stuff that we know doesn't collapse into a black hole. So our understanding of collapsing objects is pretty busted.

    The reason we think that black holes exist is that we see things that look, smell, and act like black holes. If we didn't, then it's possible that we've messed up something basic and stars just don't turn into black holes, but we do. It just so happens that 1.2 solar mass compact objects behave very, very differently than 8 solar mass objects, and the prevailing explanation is that one is a neutron star and the other is a black hole. There are no 8 solar mass pulsars that we know of.
     
  16. May 8, 2010 #15
    You can go to Kip Thorne's publications page

    http://www.its.caltech.edu/~kip/scripts/publications.html

    The main paper is here

    D. Macdonald and K.S. Thorne, "Black-Hole Electrodynamics: An Absolute-Space/Universal-Time Formulation," Monthly Notices of the Royal Astronomical Society, 198, 345-382 (1982).

    http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1982MNRAS.198..345M

    Yes. Quasars and AGN have very strong magnetic fields. The prevailing view is that it comes from the black hole that's in the middle of them. You can jump up and down and scream, quasars and AGN have strong magnetic fields in them, and the general response to that is "yes we know that."

    Also Kip Thorne wrote an excellent article about this mechanism in Scientific American in 1988 back in the days when SciAm was a real science magazine.

    Now if you have any good reasons for thinking that Kip Thorne is wrong and that his mechanism just will not work, then that would be an interesting topic for discussion.
     
  17. May 8, 2010 #16
    One other thing is that I don't think that you can stop a collapse by magnetic pair-production. The problem is that if you have enough energy to produce electron-positron pairs, you have enough energy to produce neutrino/anti-neutrino pairs.

    Also pair-production tends to destabilize a star rather than to destabilize it...

    http://en.wikipedia.org/wiki/Pair-instability_supernova

    There's all sorts of interesting, poorly understand physics going on here. If you just go with the theory, then it's not obvious that black holes can form, but the idea that black holes exists comes from things like Cygnus X-1 which looks, smells, and tastes like a black hole. If you can come up with smoking gun evidence that high mass compact stars are not black holes that would be interesting, but the fact that AGN's and quasars have strong magnetic fields is not this sort of evidence.
     
  18. May 8, 2010 #17
    The basic thing that I just don't understand which someone needs to explain to me is why Schild seems to think that black holes can't have strong intrinsic magnetic fields. I can point to Kip Thorne's papers in which he describes how black holes can generate huge magnetic fields.

    If you can point to some argument that goes through Thorne's mechanism and shows that he is simply wrong (i.e. something along the lines of what Michel did with the GJ model), and that black holes simply cannot generate massive magnetic fields, then that changes things. Until then, it's really, really hard for me (or most people in the field) to take Schild's assertions seriously.

    When I look at the papers you have referenced, it looks to me that the MECO's he is describing are in fact black holes, and someone needs to explain to me why the object he references in his papers aren't black holes.
     
  19. May 8, 2010 #18
    Here is a review paper on black hole magnetospheres...

    http://arxiv.org/pdf/0909.2580

    If you go www.arxiv.org and type in "black hole" and "magnetic field" you get 842 hits.

    What it boils down to is that Schild seems to think that the fact that AGN and quasars have very strong magnetic fields some how disproves the idea that they are powered by black holes. What I don't understand is why Schild seems to think that black holes can't have strong intrinsic magnetic fields when no one else seems to have any problem with the idea.

    Before we go any further, I'd really like to understand why he seems to think that. This isn't a rhetorical statement. It's really like to understand what he is asserting.
     
  20. May 8, 2010 #19
    There is something that limits black hole growth to 10^10 solar masses. As noted in this quasar survey summary the quasar massive object's mass at z approx. 6 is at most a few 10^10 solar masses. There are no larger super massive objects at any redshift than a few 10^10 solar masses.

    Note if dark matter exists the problem becomes more difficult to explain as the black holes should overtime gain mass due to dark matter. They do not which appears to indicate dark matter does not exist and the massive object has a property that it stop mass gain and/or lose mass.

    The are the peculiar fountain of youth stars that orbit the Milky Way's massive object and curiously also orbit Andromeda's massive object. They are called the fountain of youth stars as they have very short lifetimes do to there size and high temperatures.

    Somewhat puzzling is how does one explain the Milky Way's center's massive object's 3.6 x 10^6 solar masses (BH were 10^10 solar masses at z=6) and Andromeda's 30 x 10^6 solar masses. The Milky Way is a relatively large galaxy.

    There is also the interesting hypervelocity stars that are also massive hot short lived stars that have speeds in excess of the galaxy's escape velocity.

    These hot short lived stars appear to be special stars that have a much longer lifetime than other similar hot stars in the galaxy.

     
  21. May 8, 2010 #20
    Can we focus on mystery at a time :-) :-) :-)

    One problem with astrophysics is that there are so many things that we either don't understand or understand poorly that it's hard really have a discussion if we talk about all of them. Now it might be that a lot of the questions are connected in some way, or not.....

    I'm not sure that I see the problem here. The obvious thing that limits growth is the amount of matter it can gobble up. The totally mass of the Milky Way is 10^12 solar masses. Having the black holes sweep up all of the matter in the middle of the galaxy and then stop after eating up 1% of the galaxy seems not crazy. Also 10^10 solar mass implies about one solar mass per year which raises the question of how much gas a black hole could eat up in one year.

    Let me reverse the question. How big would you expect the AGN black holes to be?

    I'm still not sure I see the problem. Can you punch some rough numbers that illustrate the problem? You can estimate the amount of dark matter within say 1 light year of the black hole. I don't think you'll come up with a large number.

    That one is pretty easy. You take an old star, strip away it's envelope and you have a new looking star. This also seems to happen in clusters of stars.

    It's actually not. The big monster galaxies are the cD galaxies. Also, it's not clear what the relationship is between the black hole mass and the mass of the galaxy or even it there is one. One problem is that we really have no clue how galaxies formed.

    The current explanation is that a binary star got close to the black hole. Black hole ate one star, the other ran away.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: State of Pulsar Theory & Observations
  1. Binary pulsars (Replies: 1)

  2. Millisecond pulsar (Replies: 9)

  3. Pulsar's spectrum (Replies: 2)

Loading...