Neutron Star to Black Hole

Discussion in 'Astronomy, Exobiology, & Cosmology' started by RajeshTrivedi, Jan 12, 2015.

  1. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    The Schwarzschild Black Hole is non rotating type, but other solution like Kerr BH is a rotating type.

    Case 1: The BH is formed either on account of collapse of a very big star (M >> TOV Limit) or
    Case 2: on account of accretion of mass by a Neutron Star such that its mass becomes > TOV Limit.

    This modified TOV limit is taken at around 3 Solar Mass. Theory also says that formation of BH is dynamically timed that is it takes less than a second to form a BH once star is inside EH.

    Q1. In general the Rotational Kinetic Energy of the Neutron Star is of the order of 10^40 Ergs. So in case Schwarzschild BH is formed due to accretion of mass by Neutron Star, then what happen to this Rotational Kinetic Energy ?

    Q2. In case of Kerr BH which is rotating type, what rotates ? The mass is at singularity, Ergosphere also cannot be stated to have this energy or mass, then what rotates ? For clarity the mass/energy here is the original BH formation mass/energy...not what is acquired due to accretion.

    Q3. What do we really mean by non rotating Schwarzschild BH or Rotating Kerr BH, when the inside of EH itself is not interacting with Physical World.
     
    Last edited: Jan 12, 2015
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. paddoboy Valued Senior Member

    Messages:
    21,434
    In essence it is thought that gravity will always win out. A Schwarzchild metric BH would not form. This was mentioned in the last thread re BH's, obviously you weren't listening.
    It would be a Kerr or other variety.

    Again, as explained to you in the other BH thread, the entire mass of any BH resides at the Singularity/quantum/Planck scale. The rest is just critically curved spacetime.
    What rotates? The BH [spacetime] within the EH rotates, to form the ergosphere you speak of, and the mass at the Singularity rotates to form a "ring Singularity"
    Is there a limit to the spin? We are not sure, but most mainstream cosmologists accept the notion that there is certainly a limit to spin, otherwise the dreaded "naked Singularity" could arise.
    Perhaps the outer horizon is limited somewhat in spin, when its spacetime parameters touch the polar regions of the inner EH.
    It's also been theorised that any fast spinning BH, may just hurl matter/energy away, before it crosses the inner EH.
    In essence, and most probably, there would always be some limitation to a BH's spin or some other aspect, to stop it flying apart.
    Worth noting also as mentioned in the other thread, energy can be extracted in certain circumstances from within the ergosphere.
    Also don't forget that spacetime outside any BH ergosphere would also be spinning [ frame dragging]


    You have already been informed about the standard Schwarzchild BH, and its general usage for simplification.
    A Kerr type BH spins.
    A Kerr-Newman BH is a charged rotating BH.
    A Reisner-Nordstrom BH is a charged non-rotating BH.
    Nothing within the EH of any BH interacts with outside. So what are you suggesting?


    Some nice links about BH's
    http://casa.colorado.edu/~ajsh/home.html
    http://casa.colorado.edu/~ajsh/relativity.html

    http://csep10.phys.utk.edu/astr162/lect/blackhole/blackhole.html

    http://cosmology.berkeley.edu/Education/BHfaq.html
     
    Last edited: Jan 12, 2015
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    If I understand correctly Ergosphere is the outer part of oblate sphere (external to EH sphere not within)....Further again if I understand correctly the ring singularity is at r = Rs (at EH surface) which is chosen coordinate system specific. The singularity at r = 0 is not the ring singularity. Moreover spacetime within EH cannot be rotating. Please correct me if my understanding is wrong.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. brucep Valued Senior Member

    Messages:
    4,098
    Read Project F "The Spinning Black Hole". The ring singularity, predicted by General Relativity, is a direct consequence of the rotation. The Kerr metric reduces to the Schwarzschild metric when the black hole is no longer rotating. Fun read.
    http://www.eftaylor.com/download.html
    BTW Chapter 2 "Curving" introduces the Schwarzscild metric solution to the Einstein Field Equations for parameter spherically symmetric non rotating.
     
    Last edited: Jan 12, 2015
  8. paddoboy Valued Senior Member

    Messages:
    21,434

    WRONG
    The ergosphere exists between the EH proper, and the oblateness outer EH dictated by the BH's spin.
    The ring Singularity is not at the EH.
    The ring Singularity is in the middle.
    The ring Singularity would reduce to r=0 once spinning stopped.
    Spacetime within the inner EH, spacetime between the inner and outer EH are certainly spinning, as well as spacetime outside the outer EH or ergosphere.
    Ever heard of frame dragging? or the Lense-Thirring effect?
    Even spacetime around the earth spins.
     
    Last edited: Jan 12, 2015
  9. OnlyMe Valued Senior Member

    Messages:
    3,914
    Unless the black hole is connected in some way with what lies outside the event horizon, what is there to cause it to spin down, so to speak. If there is no energy transfer from inside to outside the event horizon all angular momentum within the event horizon must be conserved, no?
     
    Last edited: Jan 13, 2015
    KilljoyKlown likes this.
  10. paddoboy Valued Senior Member

    Messages:
    21,434

    All the EH is, is critically curved spacetime, and a parameter where the escape velocity equals "c".
    For any Kerr BH to spin down, [and I wasn't inferring that] I would surmise swallowing matter/energy of a certain trajectory...Simarily, any magnetic field would be negated by attracting opposite charge.
     
  11. KilljoyKlown Whatever Valued Senior Member

    Messages:
    6,493
    A Schwarzschild Black Hole doesn't really exist in reality, so I've often wondered how fast a tiny BH inside an event horizon might be rotating? To give you a feel for what I'm talking about the fastest rotating neutron star known so far is.

    http://www.space.com/3482-star-shatters-spinning-speed-record.html

    I believe the average neutron star is about 20 miles in diameter, so any point on the surface will be moving at about 70,461 miles/sec. The smaller the diameter the faster the rotation speed will be. Assuming a stellar size BH is not a true singularity, it will still have a much smaller diameter than the neutron star and have an outrages spin rate.
     
  12. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    Thanks...referred to the link, but they do not answer the questions stated in op.
     
  13. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    Paddoboy,

    Small digression is necessary to enable focused discussions on the questions of OP and to minimize the confrontation.

    1. Pl refer to below link, it will throw some light on basic coordinate singularity (or ring singularity) at r = Rs. This will also clarify use of word True Singularity ar r = o in the context (non coordinate specific). [refer to Singularities and Black Hole section in the middle or so]

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

    2. Below link will define Ergosphere, which is the oblate part outer to EH (EH sphere here means r = Rs Sphere). This small link will also clarify that frame dragging and lense thirring effect is present in ergosphere. This will also give a clue that inside the EH, space time spinning is not invoked.

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

    3. Below link will clarify a process of energy transfer from BH, which you referred in your first post.

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


    With these links and questions on OP we should be at the same level on following...

    1. Drop Planck's level reference, as that is the part of future QGT and nothing to do with these BHs as on date.
    2. EH reference is to the r = Rs.
    3. Ergosphere is the part of oblate sphere region external to EH, even if polar radius is smaller than Rs.
    4. Frame Dragging and lense thirring effect is present inside ergosphere, not inside EH.
    5. Energy transfer is possible through ergosphere, but only during possible accretion. (Penrose)
    6. Inside of EH spins or not, we do not know (in all likely-hood it cannot), because Kerr BH/Penrose talk about rotational energy in Ergosphere, implying that we do not know inside of EH with respect to spin part as well.


    Correct me rationally if I am wrong, and also please edit both your posts, because there are certain apparent inaccuracies.

    After that we will focus on the questions.
     
  14. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    True....But it is hypothesized that a Kerr BH (Spinning) will loose its rotational energy due to reverse Penrose Process and a time would come when BH will be without spin, thus forming a Schwarzschild BH...Since Penrose talks about even increase of rotational energy of Kerr BH also in certain cases, so we do not really know how much time it would take a Kerr BH to become a Schwarzschild BH. So can we say in reality no Schwarzschild BH ?

    Infact this is precisely the question in the OP....What happens to the rotational energy of Neutron Star which is of the order of 10^40 at the time of its getting converted into BH through accretion ?

    {incidentally the average radius of a Neutron star is around 9-13 Kms, not around 20 miles/ 32 Kms...}
     
    Last edited: Jan 13, 2015
  15. paddoboy Valued Senior Member

    Messages:
    21,434

    Please Register or Log in to view the hidden image!

    GR predicts compulsory collapse to Singularity/Planck/quantum status.
    Singularities are present in BH's.
    Now if you want to continue along that line again, then take it to the other thread. Planck/Quantum levels and Singularities will be correctly referenced when and If I see fit. Thank you.

    The EH of any BH is accepted in general to be that parameter [as I have stated before] where spacetime curvature status reaches a stage where escape velocity is "c"
    It is also the Schwarzchild radius.

    ??? The ergosphere is as stated and bound by the outer oblated parameter depended on rate of spin, and the inner EH [or Schwarzchild radius]

    Obviously English appears to be your second language.
    Please read my reply again.....
    NOTE WHERE I SAID "AS WELL AS SPACETIME OUTSIDE THE OUTER EH OR ERGOSPHERE. EVEN SPACETIME AROUND THE EARTH SPINS"

    Energy transfer is possible within the ergosphere..thank you, that's what I said.

    Spin of spacetime within the EH proper in all likelyhood is correct. Considering of course that all the BH is spinning, and we have a ring Singularity.


    Corrected! Edits though not required thank you.

    That depends on whether I chose to ignore your apparent arrogance and posturing in telling me what to do.
    Now you have numerous reputable links, including brucep's.
    Read them all carefully, then come back, and I'll decide where this stuff is at.
    Thank you.
     
    Last edited: Jan 13, 2015
  16. paddoboy Valued Senior Member

    Messages:
    21,434

    You have already been told that the Schwarzchild metric is used for ease of conveniance.
    Irrespective most BH's will certainly be Kerr or one of the other varieties as any negation in spin would probably take a long long time.
     
  17. paddoboy Valued Senior Member

    Messages:
    21,434
    It would also be rather wise to read your own link, or if you have, then to try and interpret it correctly.

    EXCTRACT:
    Within the ergosphere, spacetime is dragged along in the direction of the rotation of the black hole at a speed greater than the local speed of light in relation to the rest of the universe. This process is known as the Lense-Thirring effect or frame-dragging.[2] Because of this dragging effect, objects within the ergosphere could not be stationary with respect to the rest of the universe unless they were to travel faster than the speed of light with respect to local spacetime. A suspended plumb, held stationary outside the ergosphere, will experience infinite/diverging radial pull as it approaches the static limit. At some point it will start to fall, resulting in gravitomagnetically induced spinward motion. Another result of this dragging of space is the existence ofnegative energies within the ergosphere.

    The outer surface of the ergosphere is called the static surface. At the static surface, a particle, moving against the flow of space at the speed of light, is static relative to a distant observer. This is because the space here is being dragged at exactly the speed of light relative to the rest of space. Outside this surface, space is still dragged, but at a rate lesser than the speed of light.
    http://en.wikipedia.org/wiki/Ergosphere
     
  18. paddoboy Valued Senior Member

    Messages:
    21,434
    You may also be confused somewhat in me inferring the parameter of the outer part of the ergosphere as the outer EH.
    The WIKI link refers to that as the "static limit" but I certainly have seen the "outer EH" terminology used.
     
  19. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    Paddoboy,

    I am not interested in what you decide and what not.....You do not seem to grow up and always ready to confront despite polite nudging...

    You deserve Noble Prize for declaring that mass at the singularity is rotating...

    This is ok now, in earlier post you indicated existence of ergosphere inside proper EH, later on edited, may be poor use of words...I will let it pass.

    I thought you have understood singularities but not admitted during last thread discussion possibly due to inflated punctured ego. But it was a judgmental error on my part. You still do not know what is Ring Singularity and True singularity. 3rd statement is pure BS. Second statement is dummy, and first statement is outright incorrect.


    Again you should be awarded noble prize for such an affirmative statement that Space Time within inner EH is spinning.....what is compulsory collapse inside EH ? Link the two statements to claim your Noble.

    Language problem ?? I will let it pass.

    Why only outside ? Why not inside Ergosphere ? The statement is correct, but contextually exposes you.

    And the last but the very big sour point of yours.................True, GR predicts compulsory collapse to singularity at r = 0, but GR does not predict this at Planck's/Quantum level. Get this in your head.....I gave you a way out in last thread that may be QGT as and when it comes may reconcile with this singularity...but till then keep this singularity away from Planck's / Quantum level. You are spreading misinformation in this forum, which can be classified as trolling, my polite nudging that lets drop this issue did not work....as soon as you drop your Ego, this singularity will also drop from Planck's level.


    It is my suggestion to you.......do not take any assumed know-all position. Stop acting like a resident teacher....be a student most of the time.....
     
  20. paddoboy Valued Senior Member

    Messages:
    21,434
    And I'm certainly not interested in what you decide or to mentally manufacture as real.
    Start reading a few links.

    No, just recognition in correcting your own misconception that spacetime within the EH did not rotate.

    Rubbish. That is either an outright lie, or just your continued misrepresentation of what others have been trying to tell you.


    I do understand Singularities to a reasonable level, but unlike you, I do not have any ego to bruise, nor am I trying to update/modify any mainstream cosmology.
    All those statements are correct. But as usual, all you need is a reputable link to confirm your unsupported amateurish position.
    Let me restate, the Singularity, ring or Schwarzchild is at the center of the BH.
    The Kerr ring singularity will reduce to the Schwarzchild if spin is negated, and the Schwarzchild will take on ring topology if the BH gains spin.
    Again, if you have trouble understanding or accepting those facts, then give us a reference or link supporting whatever it is you are claiming.



    Your ignoring of pertinent information is in line with theorist constant, who just had his nonsense removed to the fringe.
    Compulsory collapse once the Schwarzchild radius is reached has been explained to you in the other thread where you once again displayed your inept attitude for understanding, your cherry picking of isolated sentences, and some obvious porky pies.


    That's not my concern.


    As English is your second language, perhaps you are unaware of what "also" means? It's similar in meaning to "as well"


    Let me make it quite clear. The Singularity region is at the Planck/Quantum scale...GOT IT?
    And no amount of posturing, and false pretense from you will change that.
    As I said, and as you proved in your last series of debacle posting in the other thread, that is the situation.
    No one as yet supported your denial of that, while I have given at least 6 links.
    You subsequently refused to offer any links in your support, ranting on about "thinking for one's self", just as that other poster theorist constant was keen to do.
    More correctly you were unable to find anything to support your stance, until an out of context snippet from one of the professors.
    My stance never once altered in that thread, but I did grow rather tired of your silly incessant, irrelevant off topic remarks and claims


    It is my suggestion to you, that you are now cunningly and deceivingly trying to turn the tables.
    I'll stand by all the posts I have made here and the other thread, just as you most certainly will have to.
    And that to any reasonable logical person, will show who was acting "teacher" and posturing with inflated ego.
     
  21. paddoboy Valued Senior Member

    Messages:
    21,434

    Let me add....
    Sometimes science is lazy in the language it uses.
    A Singularity in itself does not imply Infinite quantities. It may though lead to infinite quantities such as spacetime curvature and density.
    A quantum gravity theory is hopeful though of getting rid of the Singularity, or possibly pushing it back further.
     
  22. RajeshTrivedi Valued Senior Member

    Messages:
    1,415
    Paddoboy,

    You have decided to self goal....

    All are pretty simple statements from you, that spacetime within EH spins.....so are you changing your stand that you goofed up ?? If you are right then you are proving existence of 'causality violation' inside EH....Noble sooner or later for you ??

    So you wish to continue with above gems of statements ? Or here also you would like to change your stand ?...Just google Ring Singularity and give a single link (even of cesspool of any forum) which has any similarity with your statement #3...

    Language softened a bit still ego coming in between...

    Can you ignore below explanation (True NE Real), (this is not mine also..)

    Try putting r = Lp and show that the invariant has become singular.....then I will agree that your singularity is at Planck's level...otherwise you are just fooling yourself, no one else..

    ....................The case r = 0 is different, however. If one asks that the solution be valid for all r one runs into a true physical singularity, orgravitational singularity, at the origin. To see that this is a true singularity one must look at quantities that are independent of the choice of coordinates. One such important quantity is the Kretschmann invariant, which is given by

    Please Register or Log in to view the hidden image!



    ..........................


    Or can you question Prof Carlip when he said...


    Singularity is at a much lower level than Plank/Quantum scale....


    [I will be fair and concur with you as and when QGT comes, may be singularity can be resolved at quantum level or Planck's level or any other level.. But we do not know anything yet.]


    What qualification you possess to make a statement on behalf of Science ??? This is scandalous statement..just withdraw it...and do not mix up or boast of your linguistic expertise whatever you possess......stick to science if you can....Just stop trolling and let others focus on the substantial topics...

    My request to the mods and other knowledgeable members...let not a single incorrect statement (substantial to the point) go unnoticed, certainly not from those who attempt to offer opinion on a point...
     
    Last edited: Jan 13, 2015
  23. brucep Valued Senior Member

    Messages:
    4,098
    You need to read more than what I linked for you. Pretty sure you didn't read the project beyond looking for quotes that fit your illiterate position.
    Answer to question one. The spinning neutron star can't collapse to a spherically symmetric non rotating object because it's angular momentum will be conserved during the final collapse to a ROTATING BLACK HOLE WITH ANGULAR MOMENTUM. The rotation parameter is the angular momentum. It's what makes the Kerr geometry [spacetime] different from the Schwarzschild geometry. Clearly you didn't read the project I linked for you.
    Answer to question two. The entire Kerr geometry rotates. Clearly you didn't read what I linked for you or this would have been OBVIOUS to you. Maybe not since you don't even understand that angular momentum is always conserved. Duh!
    My answer to question three. Get a clue. You don't understand what rotation is? Clearly you didn't read the project on spinning black holes. Which makes you a lying troll in my estimation.
     
    Last edited: Jan 13, 2015
    paddoboy likes this.

Share This Page