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Thread: Another central Milky Way massive black hole?

  1. #31
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    Quote Originally Posted by Dave Lee View Post
    Now, by adding the magnetohydrodynamics in Accretion disk, what might be the effect on the Velocity?
    Is it going to change the speed? If so, increase or decrease?
    Both. And reverse it. And turn it round. It is a bit like asking if a turbulent wind will increase or decrease the rate at which a leaf falls to the ground.

    However, if it change the speed of matter, than by definition it effects the gravity force.
    It doesn't. It is just another complex set of forces that affect the motion of the material in the accretion disk. Gravity still works the same way. You wouldn't say that your chair affects the force of gravity, would you.

    So please, can we assume that the magnetohydrodynamics can't have any effect on the speed of matter in the Accretion disk?
    That is like asking can ignore the winds in a hurricane, and just assume the rain will fall straight down.

    "The accretion disc is surrounded by moving gas clouds and encircled by a large torus of gas and dust. Very fast (almost speed of light) jets emerge from many AGNs."

    So, can we assume that this almost speed of light ONLY depends on gravity force?

    If no, what might be the impact of magnetohydrodynamics in Accretion disk on this velocity?
    That is describing jets moving away from the black hole at nearly the speed of light. So:

    1. It doesn't say the accretion disk is moving at the speed of light. (Although it might be, in places. I don't know.)

    2. As the jets are going outward, that cannot be due to gravity so we can't ignore MHD - it is what is driving the jets. (In complex ways that are not fully understood.)

  2. #32
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    Quote Originally Posted by Dave Lee View Post
    http://www.scholarpedia.org/article/Accretion_discs

    "The accretion disc is surrounded by moving gas clouds and encircled by a large torus of gas and dust. Very fast (almost speed of light) jets emerge from many AGNs."
    This says nothing about the accretion disc. It says something about jets, not about discs. They are two different things.

    (ETA: as Strange also said)
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  3. #33
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    Quote Originally Posted by Dave Lee View Post
    Thanks

    Your message is clear.
    In any case, I do not try to argue, I just try to get better understanding.
    Sorry if I ask too many or too difficult questions.
    I do appreciate the great support.
    Just to clarify further.... it is not that you ask too many or too difficult questions. It is that you are framing your questions with assumptions that are clearly against the mainstream, or that you are "asking"
    for people to prove or disprove things you are proposing that are clearly not mainstream. For example:

    Quote Originally Posted by Dave Lee View Post
    <snip>
    However, if it change the speed of matter, than by definition it effects the gravity force.

    Therefore, we need to change the gravity formula so it represents the change of the velocity due to the magnetohydrodynamics in Accretion disk.

    Could it be that this is a real violation of the gravity formula?
    So please, can we assume that the magnetohydrodynamics can't have any effect on the speed of matter in the Accretion disk?
    Yes, two of those sentences end in question marks, but you are not really asking about mainstream science. You are proposing non-mainstream ideas (like MHD does not effect the speed of matter in the disk)
    and asking for consent. That is essentially advocating an ATM idea.
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  4. #34
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    Quote Originally Posted by Dave Lee View Post
    Newton Formula:

    Please advice if I understand you correctly:

    1. The Newton formula is perfectly OK to extract Central mass from orbital cycle based on real value verification for R (radius) and V (Velocity).
    2. However, as the accretion disK is very complex, we can't verify the correct values for R and V.
    That is correct. Just like you cannot use Newton's laws of motion alone if there are strong magnetic or electric effects.

    Quote Originally Posted by Dave Lee View Post
    If that is correct, Let's try to understand how the complexity effects the formula.
    So, lets start by
    magnetohydrodynamics in Accretion disk
    This is quite complicate. I need further explanation.
    Magnetohydrodynamics is a post graduate study subject, if you are going to do it in detail. It is sufficiently complex that you need good grasp of fluid mechanics, plasma physics and electromagnetic theory to get started. Even without reading ahead I know what is coming so I will say this now: You are not going to get a simple, one line answer to this question. To get to the right answer you need computer modelling, large amounts of it. That is why I linked to a paper about the modelling of accretion disks in post 21.

    Quote Originally Posted by Dave Lee View Post
    Lets assume that the accertion disc is not complex. There is no magnetohydrodynamics or any other effect.
    In this case it is quite clear that the Velocity of the matter is a direct outcome of the total mass of the SMBH and R.
    Now, by adding the magnetohydrodynamics in Accretion disk, what might be the effect on the Velocity?
    Is it going to change the speed? If so, increase or decrease?
    Would you also like to assume the Earth is flat or that the sky is a painted dome? Your assumption is unrealistic and serves no purpose in illuminating this topic. As I said the effects of MHD are complex. Some of the gas will speed up, some will slow down. Some will get caught up in flares.

    Quote Originally Posted by Dave Lee View Post
    However, if it change the speed of matter, than by definition it effects the gravity force.
    Therefore, we need to change the gravity formula so it represents the change of the velocity due to the magnetohydrodynamics in Accretion disk.
    No, this is ... this isn't even logic! The effects due to gravity remain the effects due to gravity. Adding MHD modifies the result but has no effect at all on the theoretical framework underlying gravity. You may as well say that because I can throw a ball in the air we need to change the laws of gravity.

    Quote Originally Posted by Dave Lee View Post
    Could it be that this is a real violation of the gravity formula?
    No, it is taking into account more than one effect. I honestly don't see how you can conclude that because there are things other than gravity involved gravity has to change.

    Quote Originally Posted by Dave Lee View Post
    So please, can we assume that the magnetohydrodynamics can't have any effect on the speed of matter in the Accretion disk?
    This is also broken logic. And trivially proven wrong. If gravity was all there was we wouldn't see flares, jets or emission due to inspiral.

    Quote Originally Posted by Dave Lee View Post
    With regards to the velocity of matter in the accretion disc:
    Please see tread 19:

    http://www.scholarpedia.org/article/Accretion_discs

    "The accretion disc is surrounded by moving gas clouds and encircled by a large torus of gas and dust. Very fast (almost speed of light) jets emerge from many AGNs."
    As others have pointed out - this is about jet. It is completely irrelevant to the speed of the infalling matter. As the jets are accelerated by a mix of MHD and GR effects.

    Quote Originally Posted by Dave Lee View Post
    So, can we assume that this almost speed of light ONLY depends on gravity force?

    If no, what might be the impact of magnetohydrodynamics in Accretion disk on this velocity?
    Is it going to increase or decrease?
    I've pointed out the issues with your arguments above. These questions are either of the "Summarise all of the effects of quantum physics in one sentence" type or based on chains of reasoning that don't work.

  5. #35
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    Thanks for the productive answers.

    With regards to the velocity of matter in the accretion disc:
    http://www.scholarpedia.org/article/Accretion_discs
    "The accretion disc is surrounded by moving gas clouds and encircled by a large torus of gas and dust. Very fast (almost speed of light) jets emerge from many AGNs."

    Quote Originally Posted by Shaula View Post
    As others have pointed out - this is about jet. It is completely irrelevant to the speed of the infalling matter. As the jets are accelerated by a mix of MHD and GR effects.
    O.K.
    If I understand it correctly:
    Jets emerge from many AGNs at almost speed of light, and it is accelerated by a mix of MHD and GR effects.
    In other words, you don't see any connection between the orbital velocity of the palsma in the accretion disc to this jet.

    So, how can we verify the orbital velocity of the plasma?

    Let me offer an example:
    Lets assume that there is a spinning wheel.
    We have no technology to measure its spinning velocity.
    But we have the technology to monitor an outflow jet from that wheel.
    So, how can we find the spinning velocity of that wheel?

    I have an Idea.
    If we drop water on the spinning wheel, we can get an outflow jet of water from the wheel.
    however, it is expected that this water jet must be fully tangent with the direction of the spinning wheel.
    Now, with that knowledge, let's look again on the jet which emerge from many AGNs.

    We can't drop water on the spinning accretion disc, but we can monitor a jet of dust which outflow from the accertion disc.
    So now we need to verify if that outflow jet is it fully tangent with the direction of the spinning accretion disc, or is it verical to the disc?
    If it is vertical, than it is clear that it can't give any real information about the spinning accretion velocity.
    However, if it is tangent with the spinning accretion than we use it.

    I couldn't find an answer for the direction of that jet.
    However, I have found the following article:

    the Accretion disk
    https://arxiv.org/pdf/1701.04627.pdf

    On the other hand, our simulations cannot explain some observables. For example, (Calvet et al. 1993) have estimated an outflow rate of 10−5M yr−1 for FU Ori which has an accretion rate of 2 10−4M yr−1 . In our simulations, the outflow rate from R=0.5 to 5 is only 0.4% of the accretion rate, while observations suggest that the outflow rate is 5% of the accretion rate. One solution is that the outflow originates from a wide disk range (from the stellar surface to 1 AU). Another solution is that the disk is threaded by a stronger net vertical magnetic fields. Strong magnetic fields have been observed in FU Orionis system (Donati et al. 2005).

    It is stated clearly that our scientists expected to see a very low outflow jet of about 0.4% from the accretion disc, but they have discovered that it is as high as 5%.
    It is also stated that the disk is threaded by a stronger net vertical magnetic fields.
    So, does it mean that the outfow Jet is also moving vertically to the disc or does it mean that a vertical magnetic fields force the jet to move tangent with the spinning accretion disc?
    Last edited by Dave Lee; 2017-Dec-07 at 04:43 PM.

  6. #36
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    Quote Originally Posted by Dave Lee View Post
    O.K.
    If I understand it correctly:
    Jets emerge from many AGNs at almost speed of light, and it is accelerated by a mix of MHD and GR effects.
    In other words, you don't see any connection between the orbital velocity of the palsma in the accretion disc to this jet.

    So, how can we verify the orbital velocity of the plasma?
    If it is resolved, spectroscopically. Modelling also helps. Tracking the motion of flaring parts of the disk. There are methods, but they are complicated by the highly dynamic and complex nature of the area around the core. Lots of inflowing gas, twisted magnetic field lines, dust etc etc.

    Quote Originally Posted by Dave Lee View Post
    If it is vertical, than it is clear that it can't give any real information about the spinning accretion velocity.
    It is perpendicular to the plane of the accretion disk, or nearly so. So it doesn't act like a wheel throwing out water at all.
    See: https://en.wikipedia.org/wiki/Astrop...ativistic_jets
    https://en.wikipedia.org/wiki/Accret...n_disk_physics

  7. #37
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    Quote Originally Posted by Shaula View Post
    If it is resolved, spectroscopically. Modelling also helps. Tracking the motion of flaring parts of the disk. There are methods, but they are complicated by the highly dynamic and complex nature of the area around the core. Lots of inflowing gas, twisted magnetic field lines, dust etc etc.

    Thanks
    It is perpendicular to the plane of the accretion disk, or nearly so. So it doesn't act like a wheel throwing out water at all.
    See: https://en.wikipedia.org/wiki/Astrop...ativistic_jets
    https://en.wikipedia.org/wiki/Accret...n_disk_physics
    I have just noticed that the article is about - active galaxies, radio galaxies or quasars.

    However, we discuss about accretion disk in spiral galaxies (Milky Way, andromeda and so on).

    Hence, do we see any kind of outflow jet from the accretion disk in spiral galaxies?
    If so, is it also prependicular to the plane of the accretion disk?

  8. #38
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    In the following article about SMBH in spiral galaxy it is stated:
    https://en.wikipedia.org/wiki/Supermassive_black_hole

    Some of the best evidence for the presence of black holes is provided by the Doppler effect whereby light from nearby orbiting matter is red-shifted when receding and blue-shifted when advancing. For matter very close to a black hole the orbital speed must be comparable with the speed of light, so receding matter will appear very faint compared with advancing matter, which means that systems with intrinsically symmetric discs and rings will acquire a highly asymmetric visual appearance.

    So can we understand that the orbital speed of matter close to the black hole is almost (or comparable) to the speed of light?
    If so, what do the mean by "very close".
    Please be aware that they do not speak about the accretion disc (no accretion disc - no MHD).
    Therefore, if we can find the radius of that matter orbital cycle and we know that it is already comparable to speed of light (and hopefully, there is no MHD) than why can't we use Newton formula to extract SMBH mass?
    Last edited by Dave Lee; 2017-Dec-07 at 08:08 PM.

  9. #39
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    Quote Originally Posted by Dave Lee View Post
    If so, what do the mean by "very close".
    The Wikipedia authors mean really, really close to the speed of light . If you want to find the actual speeds than that would be in the scientific literature.
    Even in a "spherical cow" approximation that ignores the existence of the rest of the accretion disc, using any Newton formula is wrong. We have a relativistic mass orbiting a supermassive black hole. Relativistic velocity + possible strong gravitational field = Newton is invalid.

  10. #40
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    Quote Originally Posted by Dave Lee View Post
    Hence, do we see any kind of outflow jet from the accretion disk in spiral galaxies?
    If so, is it also prependicular to the plane of the accretion disk?
    Jets can occur with just about any black hole. They are always close to perpendicular. Possible SgrA* jet: http://chandra.harvard.edu/photo/2013/sgra/

    The article I linked to covered this question (my bold):
    Relativistic jets are beams of ionised matter accelerated close to the speed of light. Most have been observationally associated with central black holes of some active galaxies, radio galaxies or quasars, and also by galactic stellar black holes, neutron stars or pulsars.

  11. #41
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    Quote Originally Posted by Dave Lee View Post
    Therefore, if we can find the radius of that matter orbital cycle and we know that it is already comparable to speed of light (and hopefully, there is no MHD) than why can't we use Newton formula to extract SMBH mass?
    If there is no accretion disk what matter are you talking about observing?

    Plus - the matter in an accretion disk is falling in. It is not in a stable orbit. Depending on the density of the matter and other effects the speed of the gas as it crosses the event horizon can vary. It is not c, as you claimed most of the available material said. It is high.

    As I have said a fair few times now. Newton's laws are too simple for this situation. You need GR and MHD. I'm not going to engage any more with you on this topic. Simply because it is clear that you are not listening, you are not reading most of the more advanced material being posted and you are determinedly ignoring the majority of what is said in order to insist on your highly simplistic models. And, frankly, I am bored of rehashing the same argument with you over and over.

    Summary: We have a good handle on the mass of SgrA* from a couple of different methods. Direct observations of the central object are not yet accurate enough to be a better method of doing it. And simplified models filled with guesses are not better than detailed observational evidence. They are certainly not going to convince anyone that we have the mass wrong by orders of magnitude.

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