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Thread: Spiral Galaxies: Stars move inwards with constant radial speed.

  1. #31
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    Quote Originally Posted by Reality Check View Post
    ...we have measured the velocities of stars. Thus you should be able to give us the measured velocities of stars relative to the galactic center. The difficulty is converting radial (towards us) and proper velocities into velocities in/out of the galactic center.

    ETA: May not be relevant but we have been observing the stars around Sagittarius A* for some decades. All I have seen are stable orbits. No stars falling into Sgr A* or being ejected from the Sgr A* region.

    IF01: Please find radial velocities of stars that are directly outward from the Sun or directly inward.
    There is some evidence here:
    https://arxiv.org/abs/0803.1826 Fig 6 page 38 and Table 5 pg 59, especially column Vavg

    and https://arxiv.org/abs/1805.00275 Fig 1 page 2 and Fig 10 page 7

    and https://arxiv.org/abs/1006.0064 Fig 4.2.1 page 45, which shows stars moving in highly elliptical orbits. These three papers show that there are stars in the bulge moving in highly eccentric orbits with one star measured with radial velocity of over 400 km/s.

    The relative radial speed relative to the sun would be zero in our vicinity (in the flat region ) as the sun is moving towards the galactic centre too, at the same speed as the other stars. If we could observe a star at the opposite side of the galaxy, maybe it could be measured, but that probably hasn't been done due to the obscuring from the disc.

    Re ETA: The ones in slower, stable orbits are more likely to be identified and measured. Faster ones, plummeting into the CMO (central massive object), would not be so easy to observe. The ejections perpendicular to the disk would occur periodically, to use the pan of water analogy, when steam has escaped, there is then a delay until the pressure builds up again to give enough force to lift the plate, then there is another sudden escape of steam.
    Last edited by john hunter; 2018-Jul-05 at 05:59 AM.
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  2. #32
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    Quote Originally Posted by john hunter View Post
    There is some evidence here...
    The term radial velocity in astronomy means the velocity toward or away from the Sun. You have a "radial velocity" toward or away from the galactic center. Can you guarantee that these papers radial velocity is your "radial velocity" so that we do not waste our time reading them?

    A hint that this is actual radial velocities in the first paper Table 3 is the wide range of values and the positive and negative values (5.1 Ī 1.8, -141.9 Ī 2.1, etc.). These are stars in the "central parsec of the Galaxy".
    What does your ATM idea predict for stars in the central parsec of the Galaxy? My impression is around 100 km/s.

    Maybe change your terminology so there is less confusion - galactocentric velocity?
    Last edited by Reality Check; 2018-Jul-05 at 10:27 PM.

  3. #33
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    Quote Originally Posted by john hunter View Post
    The relative radial speed relative to the sun would be zero in our vicinity (in the flat region )....
    That is not exactly my question so I will make it clearer:
    IF01: Please find radial velocities of stars that are directly outward from the Sun as far as the outskirts of the Milky Way or directly inward as far as the galactic center.

    You should also clarify and support that "(in the flat region)" text. Do you mean in the disk, not bulge, or is this the galaxy rotation curve "flat" region (that need not be flat!). Does the Milky Way have a rotation curve with a flat region? Is the Sun in that flat region?
    The Sun is 25,000Ė28,000 light-years from the our galaxy center that has a diameter between 100,000 and 180,000 light-years. That is at most a third of the way to the galaxy outskirts. The M33 galaxy rotation curve suggests this would be just before any "flat" region.

  4. #34
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    I'm late to the party here, but I think there are some hard questions to be asked about the following in the OP:

    Quote Originally Posted by john hunter View Post
    Following the Q&A thread, here is a proposal.

    The stars in a spiral galaxy are moving at approximately constant radial speed towards the galactic nucleus.

    It's at a similar value to the tangential speed, which is also approximately constant, (flat rotation curves), meaning that the stars move at constant speed towards the centre of the galaxy.

    <snip>
    My question: where are the observations to support "The stars in a spiral galaxy are moving at approximately constant radial speed towards the galactic nucleus", with "a similar value to the tangential speed"?

    From what I've read of the rest of this thread, there's some data on stars very near SgrA*, and on the velocity dispersion of at least one bulge, but surely you have much more than this, don't you OP? In particular, data from stellar motions in galaxy disks?

    For example, what does all the MaNGA data show?

  5. #35
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    Quote Originally Posted by john hunter View Post
    Following the Q&A thread, here is a proposal.

    The stars in a spiral galaxy are moving at approximately constant radial speed towards the galactic nucleus.
    If that were true, then the "inward" velocity should get smaller and smaller as the tangential velocity given by Kepler will be smaller (that's why it is so difficult to send a spacecraft to Mercury, you have to loose a lot of "delta V").
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  6. #36
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    As I see it, the more john hunter adds to this thread, the more pathetic it gets. We can see far and wide in the halo of our galaxy and measure the pertinent Doppler shifts. With modern infrared and radio frequency techniques we can penetrate the dust and observe all over the disk, along with SgrA. We can observe unobscured spots all over galaxies such as M31. If there was a net infall of stars and gas at velocities similar to the well observed galactocentric transverse (orbital) velocity, we should have the means to detect it, and if it occurred I would expect tons of papers making a big deal of it and looking for ways to explain it.

    I am posting this for the benefit of novices who may be reading this. If john hunter remains committed to his idea for personal reasons, so be it. The progress of astrophysics and cosmology will not be adversely affected one iota.

  7. #37
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    Quote Originally Posted by Reality Check View Post
    The term radial velocity in astronomy means the velocity toward or away from the Sun. You have a "radial velocity" toward or away from the galactic center. Can you guarantee that these papers radial velocity is your "radial velocity" so that we do not waste our time reading them?
    Good point about terminology. "radial speed or velocity" on it's own, will continue to mean relative to a galactic centre. If their could be confusion 'heliocentric or galactocentric' will be used.

    Of the 3 papers linked in post 31:

    The first https://arxiv.org/abs/0803.1826 measures Heliocentrically with mean inwards of 7.8km/s, but a high dispersion of 113km/s. These are the motions seen when we look towards the galactic centre, central parsec width-ways, but not necessarily in depth (i.e stars on the other side of the bulge might not be measured).

    This is an advance, as this thread follows on from this Q&A thread https://forum.cosmoquest.org/showthr...locity-and-age and there wasn't really any evidence found for or against radial motion at that time.

    Now we have a dispersion of heliocentric radial velocities of order 200km/s.

    1) If the sun has no galactocentric radial velocity then this implies that lots of stars do, many with approx. 200km/s or more towards the galactic centre, and lots have the same value away from the galactic centre, which may have come from stars on the other side of the bulge zooming past it, missing it and heading in our direction. It shows highly elliptical orbits -some of these stars will be absorbed by the Central Massive Object (CMO) giving an average inwards radial velocity in the bulge.


    2) If the sun has say 200km/s radial velocity towards the galactic centre, then so do lots of other stars on average.

    So we can conclude that, either way, rather being in neat circular orbits there is a substantial radial component of a great many stars towards the galactic centre.

    The next two papers of post 31 refer to galactocentric radial velocity. e.g fig 10 has those words in it's heading.

    IF01: There are stars in https://arxiv.org/abs/0803.1826 table 5 page 59, which fit your "directly inwards" requirement.
    As for the rest of post 32, there seem to be inaccuracies in it.
    Last edited by john hunter; 2018-Jul-06 at 04:52 PM.
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  8. #38
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    Quote Originally Posted by Jean Tate View Post
    surely you have much more than this, don't you OP? In particular, data from stellar motions in galaxy disks?
    This evidence was discussed in https://forum.cosmoquest.org/showthr...locity-and-age but there has been no evidence for or against. It may not be easy to separate 'bobbling' from radial velocities or tangential velocities in the dispersion.
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  9. #39
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    Quote Originally Posted by tusenfem View Post
    If that were true, then the "inward" velocity should get smaller and smaller as the tangential velocity given by Kepler will be smaller (that's why it is so difficult to send a spacecraft to Mercury, you have to loose a lot of "delta V").
    The rotation curves don't follow a Keplerian decline, (as radius increases). The tangential component is approximately constant in the 'flat region' of the rotation curve. i.e. it's different for a galaxy than it is for a central point mass. About angular momentum conservation raised by Ken G and Shaula...some must be passed on to the rest of the galaxy, perhaps to the dark matter.
    "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes

  10. #40
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    Quote Originally Posted by Hornblower View Post
    As I see it, the more john hunter adds to this thread, the more pathetic it gets. We can see far and wide in the halo of our galaxy and measure the pertinent Doppler shifts... If there was a net infall of stars and gas at velocities similar to the well observed galactocentric transverse (orbital) velocity, we should have the means to detect it, and if it occurred I would expect tons of papers making a big deal of it and looking for ways to explain it.

    I am posting this for the benefit of novices who may be reading this. If john hunter remains committed to his idea for personal reasons, so be it. The progress of astrophysics and cosmology will not be adversely affected one iota.
    That doesn't sound very scientific. In https://forum.cosmoquest.org/showthr...locity-and-age there was a question which asked specifically about any evidence for or against any radial motion in galaxies. Nobody came up with evidence against radial motion. It was mentioned in that thread - that if such evidence against was put forwards, the ATM thread might be dropped. That would be a disappointment from the point of view of this ATM thread, but it's ok - that's science.

    Perhaps you should put your evidence against this ATM thread here, if you have it.

    ----------

    Also for the benefit of novices: Never be put off trying new ideas in science. Even correct ideas have had thousands of detractors. Look what happened to Galileo.
    To quote Einstein "I think and think for months and years, 99 times I am wrong, the hundredth time I am right". So give it a try, maybe you'll come up with something.

    The progress of science is more likely to be held back by closed minded people than by people trying new ideas.

    This thread will continue to be defended for a while longer yet.
    Last edited by john hunter; 2018-Jul-06 at 04:51 PM.
    "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes

  11. #41
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    Quote Originally Posted by john hunter View Post
    In the bulge things are different: the stars are in motion towards the central massive object (of mass M) and back out again, in highly elliptical orbits. Their speed naturally brings them back out to the virial radius rv, which defines the radius of the bulge from 0.5mv^2 = GMm/rv. Any clear inward motion isn't seen as stars are moving both ways.
    So the mysterious magic friction vanishes when you get to the bulge? Why? Your ideas require a completely unobserved interaction to drain angular momentum from matter, then some extra secret sauce to create higher densities to form arms, now the mysterious angular momentum eating monster doesn't work in the bulge ... Then stuff gets to the centre where another mysterious force forms a jif lemon bottle to squeeze material out via pressure, once ejected another unknown interaction causes it to swing back around and land with pinpoint accuracy on a part of the disk where it immediately does another trick with its angular momentum (and seemingly momentum this time) to rejoin the disk... Initially you claimed your ideas simplified the understanding of our galaxy. I really don't call these layers of weakly defined and seemingly arbitrary effects simpler. You need to produce some strong evidence to make this jumble of fixes more coherent.

    The pressure build up from the incoming matter causes occasional sudden 'escapes' of matter and radiation perpendicular to the disc.
    I would love to see you create a viable model for this, I really would. Because AGNs often spit out matter at significant fractions of the speed of light. A pressure based acceleration mechanism seems somewhat underpowered.

  12. #42
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    Quote Originally Posted by john hunter View Post
    That doesn't sound very scientific. In https://forum.cosmoquest.org/showthr...locity-and-age there was a question which asked specifically about any evidence for or against any radial motion in galaxies. Nobody came up with evidence against radial motion. It was mentioned in that thread - that if such evidence against was put forwards, the ATM thread might be dropped. That would be a disappointment from the point of view of this ATM thread, but it's ok - that's science.

    Perhaps you should put your evidence against this ATM thread here, if you have it.
    I stand by what I said in post 25. Your idea is at odds with mainstream celestial mechanics. My opinion remains that the burden is on you to show evidence for your ATM idea. So far I have seen none.
    ----------

    Also for the benefit of novices: Never be put off trying new ideas in science. Even correct ideas have had thousands of detractors. Look what happened to Galileo.
    To quote Einstein "I think and think for months and years, 99 times I am wrong, the hundredth time I am right". So give it a try, maybe you'll come up with something.

    The progress of science is more likely to be held back by closed minded people than by people trying new ideas.

    This thread will continue to be defended for a while longer yet.

  13. #43
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    snip.....
    Quote Originally Posted by john hunter View Post

    ----------
    Also for the benefit of novices: Never be put off trying new ideas in science. Even correct ideas have had thousands of detractors. Look what happened to Galileo.
    To quote Einstein "I think and think for months and years, 99 times I am wrong, the hundredth time I am right". So give it a try, maybe you'll come up with something.

    The progress of science is more likely to be held back by closed minded people than by people trying new ideas.

    This thread will continue to be defended for a while longer yet.
    In my opinion, your mention of Galileo's situation is a poor attempt at an analogy. Documented observations of the angular motions of the planets had been around throughout recorded history. In recent centuries Ptolemy and Copernicus had developed competing kinematic theories to interpret them. Galileo chose Copernicus and the authorities disagreed. Their heavy-handed reaction temporarily interfered with Galileo's contribution to the advance of science, but they could not conceal the evidence in the sky, which was there for anyone to measure and interpret. In contrast, you appear to be offering a conjecture about a type of rapid inward motion that would be observable by the same Doppler shift means by which we observe the familiar orbital motion, should it actually be occurring. I would continue to say that the evidence is decisively against it.

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    Quote Originally Posted by john hunter View Post
    1) If the sun has no galactocentric radial velocity then this implies that lots of stars do, many with approx. 200km/s or more towards the galactic centre, and lots have the same value away from the galactic centre, which may have come from stars on the other side of the bulge zooming past it, missing it and heading in our direction. It shows highly elliptical orbits -some of these stars will be absorbed by the Central Massive Object (CMO) giving an average inwards radial velocity in the bulge.
    It is going to be problematic to explain stars in highly elliptical orbits around the centre of the galaxy. The galaxy is not a point source of mass; its mass is distributed all the way out to the rim. So stars won't orbit it like they would a point mass.

    If they were to round the core and head back out, they would lose little velocity, since there is plenty of mass in all directions - including in front of them.

    And that also sort of shoots a hole in the idea of them gaining speed as they fall inward as well.

    Essentially, when embedded in a (lumpy) soup of mass, stars' velocities will not vary anywhere near as significantly as they would in a Keplerian orbit.

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    Quote Originally Posted by DaveC426913 View Post
    It is going to be problematic to explain stars in highly elliptical orbits around the centre of the galaxy. The galaxy is not a point source of mass; its mass is distributed all the way out to the rim. So stars won't orbit it like they would a point mass.

    If they were to round the core and head back out, they would lose little velocity, since there is plenty of mass in all directions - including in front of them.

    And that also sort of shoots a hole in the idea of them gaining speed as they fall inward as well.

    Essentially, when embedded in a (lumpy) soup of mass, stars' velocities will not vary anywhere near as significantly as they would in a Keplerian orbit.
    They can still be screaming fast in the inbound portion of an eccentric orbit, with a radial velocity inbound that is temporarily comparable to the transverse component. It will level off as it flies by the center and there will be a balancing outbound portion, resulting in the aforementioned velocity dispersion.

  16. #46
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    Quote Originally Posted by Hornblower View Post
    They can still be screaming fast in the inbound portion of an eccentric orbit, with a radial velocity inbound that is temporarily comparable to the transverse component. It will level off as it flies by the center and there will be a balancing outbound portion, resulting in the aforementioned velocity dispersion.
    1] A highly eccentric orbit won't occur in a flattish gravitational field. An infalling mass is pulled in all directions - largely canceling out the effect of a point mass at the centre. So a transverse component will cause it to simply fly by, with a modest deflection.

    2] But if an eccentric orbit did occur, it'd be a hyperbolic orbit, carrying it essentially out of the galaxy. A high speed perihelion (perigalaxion?) - in a flat gravity field - is not going to slow down appreciably on the outbound leg.

    Orbits in distributed gravitational fields simply do not behave the same as orbits around point masses.

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    Quote Originally Posted by john hunter View Post
    The rotation curves don't follow a Keplerian decline, (as radius increases). The tangential component is approximately constant in the 'flat region' of the rotation curve. i.e. it's different for a galaxy than it is for a central point mass. About angular momentum conservation raised by Ken G and Shaula...some must be passed on to the rest of the galaxy, perhaps to the dark matter.
    okay i should not have said kepler maybe (although the stars still orbit in keplerian orbits, just the mass inside the orbit is different from what we can see). but "flat" is not flat, see e.g. wiki. your moving stars have some amazing magical properties that are non physical
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  18. #48
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    For posts 41-46, Shaulas comments and how an object would move in bulge with a distributed mass of constant density rho.

    At first modelling an object moving past (and close to) the centre, at velocity v, and travelling out as far as it can until it stops. dv/dr = dv/dt*dt/dr = acc*1/v

    Which gives v dv = acc*dr . The acceleration is from -GM/r^2 is -G(4/3*pi*r*rho) so integral v to 0 of vdv = integral 0 to rv of -G
    (4/3*pi*r*rho) dr

    Where rv is the virial radius, approx. radius of the bulge (although it probably doesn't have a well defined edge)
    ....this maths is to decide how the velocity of a star changes, if 'dropped' from the edge of such a bulge and falls towards the centre.

    leaving off negative sign and switching limits, 0.5v^2= 0.5krv^2 where k= 4/3*pi*rho*G , v=sqrt(k)*rv.

    So if a star drops from rest from rv it would reach a speed v at the or near centre of v=sqrt(k)*rv.

    Since the acceleration is proportional to r, it's like SHM, with the star performing a kind of SHM motion (ignoring any tangential component) with angular frequency omega of sqrt(k).

    Incidentally, the speed reached, of such a falling star at the centre, equals the tangential velocity of the flat region of the rotation curve.

    At rv (the radius of the bulge), v*2/r = kr^3/r^2, giving the same result.

    To Shaula: There are two distinct components to the galaxy. The flat rotation curve, the bulge (also maybe the CMO), conditions are different for each, maybe more discussion on this later.
    Last edited by john hunter; 2018-Jul-08 at 10:05 AM.
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  19. #49
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    Quote Originally Posted by tusenfem View Post
    okay i should not have said kepler maybe (although the stars still orbit in keplerian orbits, just the mass inside the orbit is different from what we can see). but "flat" is not flat, see e.g. wiki. your moving stars have some amazing magical properties that are non physical
    From your and Shaulas comments you seem to saying 'magical' etc.. 'but not fully understood' seems better.

    The flat rotation curve itself is not fully understood, dark matter hasn't been detected or understood yet. To suggest that the radial motion is also constant isn't such a radical suggestion. After all, we see jets, AGNs and lobes commonly near galaxies. Where is all that matter coming from? One website said the energy in the AGN was 10^54 J Which is 10^37kg or 10 million solar masses.

    If it's coming out, it presumably goes in too...understanding how it goes in and how it's ejected seem to be the main problems.
    "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes

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    Quote Originally Posted by john hunter View Post
    If it's coming out, it presumably goes in too...understanding how it goes in and how it's ejected seem to be the main problems.
    As I have said before the issue is the number of arbitrary things in the idea. Dark matter has precisely one bit of 'magic' in it. That there is a form of matter which only interacts gravitationally. Everything else in the theory and all of the predictions that come from it are based on well understood, tested physics. Between gravity as we understand it, a few testable parameters corresponding to well understood physical properties (mass, effective temperature) and some fluid dynamics we get a reasonably good predictive model.

    The issue is that your initial claim was that your idea was simpler to understand than dark matter. But what has come out of this thread is that, even without you providing firm predictions or an actual model, your ideas actually have to be significantly more complex than dark matter and involve a range of interactions that we simply don't observe (and then a bunch of fixes to explain that away). We don't see matter inflow on the level you claim, we don't see matter outflow on the level you claim, we don't see streamers of matter falling back to the galaxy to make spiral arms. You can't explain how stars lose angular momentum (until they change their mind when they get to the bulge), you can't explain how the spiral arm density is preserved. You can't explain how the ejected material is ejected or how it is recycled.

    So unless you can provide some compelling and testable predictions that show the value of your ideas, as I have asked and you have said you are unable to do, we are left with a choice between two paradigms. One invokes a single piece of new physics and matches observations of rotation curves, cluster dynamics, structure formation and nucleosynthesis. Not perfectly, I'd never claim that, but pretty well. The other invokes at least four pieces of new physics or previously unobserved interactions* and requires they have a range of properties and behaviours that exist only to excuse away the lack of observational evidence.

    As for magical vs not fully understood ... Not fully understood is where you have at least part of the theory worked out using known physics but there is a small gap. Magical is where you invoke a whole range of apparently disconnected behaviours so that your idea remains viable in spite of physics. That is why I have used the term magical. If it had just been one of the interactions being unknown I could have agreed with Not fully understood. Where you have four I go with Magical.

    *the in-fall interaction, the filamentary interaction, the ejection interaction, the spiral arm interaction

  21. #51
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    Quote Originally Posted by john hunter View Post
    Good point about terminology. "radial speed or velocity" on it's own, will continue to mean relative to a galactic centre. If their could be confusion 'heliocentric or galactocentric' will be used.

    Of the 3 papers linked in post 31:
    Your answer is wrong. The table is "Radial Velocities of Narrow He I Line Stars". Once again that is actual radial velocities.

    The answer is in: The central velocity dispersion of the Milky Way bulge
    Fig. 10. Mean galactocentric radial velocity (top) and velocity dispersion (bottom) as a function of the Galactic longitude, for different latitude as listed in the labels.
    The actual numbers are in
    Table 3. Mean heliocentric and galactocentric radial velocity, and velocity dispersion measured for the bulge stars in the observed fields
    +9.8 135 +/- 3.1
    -8.8 125 +/- 3.3
    19.2 137 +/- 5.3
    14.7 119  /- 4.7
    Are these "directly inwards" from the Sun? I am going to say yes because the Galactic Longitude range is +/- 4 degrees. The actually direct inward measurement has a longitude of 0 and value of 19.2 km/s 137 +/- 5.3

    IF02: Please give your prediction from your ATM idea for the galactocentric radial velocity of bulge stars with a galactic longitude of around 0 ("directly inwards" from the Sun).

  22. #52
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    Quote Originally Posted by john hunter View Post
    That doesn't sound very scientific. In https://forum.cosmoquest.org/showthr...locity-and-age there was a question which asked specifically about any evidence for or against any radial motion in galaxies. Nobody came up with evidence against radial motion.
    Jens wrote that they asked the question a long time ago in Q&A "is there any evidence that galaxies are like vacuum cleaners, that pull stars into the centers, or like sprinklers that eject the stars outward?" and said that as far as they remembered the answer was no evidence for or against.

    That put the burden of evidence on you with your assertion that there was galactocentric radial velocity. A week later you give a reference that has actual galactocentric radial velocities for stars in the Milky Way bulge. This is interesting but irrelevant unless you can match it with your ATM idea.

  23. #53
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    Quote Originally Posted by john hunter View Post
    The flat rotation curve itself is not fully understood, dark matter hasn't been detected or understood yet.
    That is not correct. Galaxy rotation curves including the "flat" part (which need not be flat!) are well understood. Take the visible matter. Add a distribution of dark matter. Get good matches to the observed galaxy rotation curves, regardless of what dark matter is. We do not have to detect dark matter but we have. We do not have to detect dark matter in labs here on Earth and dark matter may not be detectable but we are trying.

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    Quote Originally Posted by Shaula View Post
    We don't see matter inflow on the level you claim, we don't see matter outflow on the level you claim, we don't see streamers of matter falling back to the galaxy to make spiral arms. You can't explain how stars lose angular momentum (until they change their mind when they get to the bulge), you can't explain how the spiral arm density is preserved. You can't explain how the ejected material is ejected or how it is recycled.
    The streamers suggestion to make the spiral arms was dropped see post 21, but the point was that an object moving with both constant radial and tangential speed traces out a spiral pattern. It is known that vt is constant so maybe vr too.

    But you are right we need to explain inflow, loss of angular momentum and ejection.

    To help discuss things here is the start of a model rotation curve.

    https://www.desmos.com/calculator/vgfa6y5gwz

    If we imagine velocity of rotation on the y axis and radius from centre on the x axis.

    The central bulge (region A), has constant density and velocity of rotation for this region is represented by y=8x.

    The flat part of the curve (region B) is represented by y=8.

    The two regions are different as in region A, according to the ATM model, stars are falling inwards as in post 48, but going past the centre and moving outwards again, as far as they can defining a radius rv of the bulge.

    On the diagram rv is x=1 and vt is y=8

    The densities of the two regions are rhoA = 3*vt^2/(4*pi*G*rv^2)
    and rhoB =vt^2/(4*pi*G*r^2)...(the r in the denominator being for any radius greater then rv) so the density of the bulge is three times the density of the flat region at r=rv.

    There is thus a discontinuity, a change of density, at rv.

    Restricting the domains according to the different conditions in the two regions...https://www.desmos.com/calculator/iz8iklkd6m

    It will be attempted later, to explain infall in region A and B towards the central massive object, also ejection form the CMO whose mass, although high, is small relative to the bulge and the whole galaxy.
    Last edited by john hunter; 2018-Jul-09 at 10:27 AM.
    "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes

  25. #55
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    Tusenfem,

    As you may know attempts have been made to contact the moderators to ask permission to briefly describe a mechanism for ejection from the centre of a galaxy. It involves concepts from an ATM thread of 2005, and there is new evidence in support of it.

    A single post should do. Would you clarify whether or not it's ok to do this.
    "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes

  26. #56
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    Quote Originally Posted by john hunter View Post
    This evidence was discussed in https://forum.cosmoquest.org/showthr...locity-and-age but there has been no evidence for or against. It may not be easy to separate 'bobbling' from radial velocities or tangential velocities in the dispersion.
    Thatís the full extent? You yourself did no independent literature searches? Did you find no astronomer who has done work that might be relevant? Did you download any data from MaNGA (say), and do your own analyses?

    I donít hang out here much, but I have to say that this ATM idea of yours seems to have had very little effort put into it, to try to find relevant data, either for or agin. It might be wise for you to ask to pause it, while you take time to do a proper literature search.

  27. #57
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    Quote Originally Posted by Jean Tate View Post
    It might be wise for you to ask to pause it, while you take time to do a proper literature search.
    Maybe, it takes a lot of time dealing with the questions...

    Following on from the graphs a couple of posts ago.
    There were two regions A and B, the steep rise y=8x and the flat one y=8, and a discontinuity where they met.

    So if galaxies have regions of two types which have to meet and end up with a smooth rotation curve, what would it look like?

    This cubic spline fitter https://tools.timodenk.com/?p=cubic-...-interpolation

    With this data
    0 0
    1 8
    2 8
    3 8
    4 8
    5 8
    6 8
    8 8
    10 8

    Gives this graph which looks reasonable.

    https://www.desmos.com/calculator/ys9xlui6cs

    So maybe we only need to explain why there is a constant density region (A), and a density region B inversely proportional to r^2, which the ATM thread might be able to do.
    Last edited by john hunter; 2018-Jul-09 at 10:17 PM.
    "...when you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes

  28. #58
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    Quote Originally Posted by Jean Tate View Post
    Thatís the full extent? You yourself did no independent literature searches? Did you find no astronomer who has done work that might be relevant? Did you download any data from MaNGA (say), and do your own analyses?

    I donít hang out here much, but I have to say that this ATM idea of yours seems to have had very little effort put into it, to try to find relevant data, either for or agin. It might be wise for you to ask to pause it, while you take time to do a proper literature search.
    For avoidance of doubt, those four questions are not rhetorical; I look forward to your answers.

  29. #59
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    Quote Originally Posted by john hunter View Post
    Following on from the graphs a couple of posts ago....So maybe we only need to explain why there is a constant density region (A), and a density region B inversely proportional to r^2, which the ATM thread might be able to do.
    First you have to supply evidence supporting your ATM idea so that your graphs are not a waste of our time. Then you have to explain the curved because this is your ATM idea. Others may chime in if they want.

  30. #60
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    Quote Originally Posted by john hunter View Post
    The streamers suggestion to make the spiral arms was dropped see post 21, but the point was that an object moving with both constant radial and tangential speed traces out a spiral pattern.
    The problem is that every star in the galaxy will follow that spiral pattern which is a very probable prediction of no spiral arms! A spiral arm is a small (10-20%) increase in density of stars and gas that leads to high star formation and the brightness of the arms making them prominent.

    You have to show that the "spiral pattern" is different for different stars in such a way that arms are created and sustained.

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