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

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.

It was the flat rotation curves which led to the 'dark matter' model, and dark matter is still required here.

However, something there doesn't seem to have been much work on, is why dark matter takes on the particular distribution it needs to have to give the flat rotation curves. This very definite distribution lacks an explanation. The proposal here can explain this distribution, details soon.

The proposal can also explain the spiral shape.

It's going to be a difficult one to defend, but maybe of interest...

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Originally Posted by john hunter
However, something there doesn't seem to have been much work on, is why dark matter takes on the particular distribution it needs to have to give the flat rotation curves. This very definite distribution lacks an explanation. The proposal here can explain this distribution, details soon.
Just a minor point - lots of work has been done on this. The pseudo-isothermal distribution and the NFW profiles both were derived from theoretical considerations. There definitely is an explanation for the coarse scale distribution. The Einasto profile is the only commonly used empirical form.

Your idea will have to perform better than the extensive simulations that reproduce these distributions.

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About the distribution of dark matter.

The v in this section is for v(t) the tangential velocity.

The flat rotation curves show a constant v, with radius (r), as for a star of mass m

mv^2/r=Gm*M(r)/r^2

where M(r) is the mass of the galaxy within radius r.

so M(r) =v^2r/G ...................... equation (1)

Now, what would be the density distribution to give the required mass distribution above?

M(r) =integral[4*pi*r^2*rho(r)]dr =v^2r/G

rho(r) must be inversely proportional to r^2, so in the integral the r terms cancel, then after integration M(r) is proportional to r

rho(r) = k/r^2 ........................ equation (2)

where k=v^2/(4*pi*G)

The proposal was that stars move inwards at constant radial speed. It is also that the dark matter is in motion, similar to the stars. This naturally gives the required density distribution of equation(2).

Imagine matter passing through a spherical shell near the outer 'edge' of a galaxy radius r(0), thickness dr, volume 4*pi*r(0)^2*dr. When the matter all moves to a smaller radius r(1), the volume has reduced to 4*pi*r(1)^2*dr and the density has increased.

For matter drifting inwards in this way, density is inversely proportional to r^2 as in equation (2).

To summarise: Matter (dark and visible) drifting inwards at constant speed, naturally gives the right density and matter distribution needed to explain the flat rotation curves.
Last edited by john hunter; 2018-Jun-28 at 06:25 AM.

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Originally Posted by Shaula
Just a minor point - lots of work has been done on this. The pseudo-isothermal distribution and the NFW profiles both were derived from theoretical considerations. There definitely is an explanation for the coarse scale distribution. The Einasto profile is the only commonly used empirical form.

Your idea will have to perform better than the extensive simulations that reproduce these distributions.
It is certainly a lot simpler and easier to understand than the above.

5. Originally Posted by john hunter
The stars in a spiral galaxy are moving at approximately constant radial speed towards the galactic nucleus.
Does this mean the galaxy will collapse after some time? How long will this take?

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You were quick Shaula, thought most people would be sleeping!

Other points: Matter reaching the centre is ejected periodically (AGNs), perpendicular to the disc.

Both constant tangential and radial velocity, v(t) and v(r), naturally give the spiral shape.

Do try this at home.

It can be shown (maths later) that the velocities above lead to a spiral shape in polar co-ordinates angle(theta) = [v(t)/v(r)]*ln(r(0)/r)

Where r(0) is a given starting radius.

choose a central point and about 16cm away have a 'starting point', move 2cm tangentially and 1cm radially. Repeat for a while and you'll see the spiral shape develop.

An alternative, similar to 'half life', with v(t)=2 and v(r)=1, is to rotate by 80 degrees each time and halve the radius, i.e. put a dot at 0 degrees r=16cm, 80 degrees r=8cm, then 160 degrees r=4cm , etc...again the spiral pattern should develop.
Last edited by john hunter; 2018-Jun-28 at 07:06 AM.

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Originally Posted by Strange
Does this mean the galaxy will collapse after some time? How long will this take?
Each object in the galaxy would reach the centre and be ejected perpendicular to the disc. Then form a spherical halo of dark matter and maybe whole stars sometimes, which gradually return throughout the galaxy but mainly at the edges. The whole system is in a stable dynamic equilibrium, so the galaxy would look the same, and last forever.

It's not too worrying for the sun though, as with v(r) of 100,000m/s and r(0) say 10^21m it's 10^16 seconds or approximately a billion years.

8. Originally Posted by john hunter
You were quick Shaula, thought most people would be sleeping!
I just wanted to comment briefly on this, because it comes up from time to time. I don't know where Shaula lives, but I am often up when people in the US are sleeping, not because I have some sleeping problem but because the sun is out here when it's night in the US.

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So how fast are stars moving towards the centre?

Is this allowed by observations?

Also, there are red dwarfs as old as the galaxy at large galactic radius.

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Originally Posted by Jens
I just wanted to comment briefly on this, because it comes up from time to time. I don't know where Shaula lives, but I am often up when people in the US are sleeping, not because I have some sleeping problem but because the sun is out here when it's night in the US.
Thought it would be night time in the US and it was 6.20am here, but there was a quick reply... there are lots of other places in the world too of course, and it was just a light hearted comment.

Kzb: The stars would be moving with a similar radial speed to the tangential speed i.e of order 100km/s. It was inconclusive in the Q&A thread whether it has or hasn't been measured. If it has and has shown for most spirals to be approx. zero, i.e. circular orbits, then the idea will be dropped.

About the red dwarves or dwarfs, maybe you could give a reference, but whole stars etc...might be ejected from the centre when they reach it, re-joining the galaxy later.

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Originally Posted by john hunter
Each object in the galaxy would reach the centre and be ejected perpendicular to the disc. Then form a spherical halo of dark matter and maybe whole stars sometimes, which gradually return throughout the galaxy but mainly at the edges. The whole system is in a stable dynamic equilibrium, so the galaxy would look the same, and last forever.

It's not too worrying for the sun though, as with v(r) of 100,000m/s and r(0) say 10^21m it's 10^16 seconds or approximately a billion years.
I can see a number of questions that I would like to see modelled.

1) Star formation. Unless you trigger it at fixed locations the spiral won't form. Take your diagram and add in a few hundred other particles that start at random locations on the disk edge. No spiral will form.
2) Angular momentum. Why are these objects shedding it? How is it lost? When things are ejected from the core perpendicularly how do they somehow change their vectors enough to get recycled into the edge of the disk?
3) AGNs are not always on. Sporadic ejections of matter, even if you can get around the recycling issue above, won't result in the smooth distribution of dark matter needed.
4) Bars. How do they fit into your model?
5) Age distribution. We see the oldest stars near the centre - if whole stars are recycled shouldn't see more very old stars at the edges? If we ignore stars and just look at the gas - we see a metallicity gradient running to the core. I.e. more metals nearer the core. Why, if this gas is being recycled? Does this gradient limit the rate of recycling consistent with it?
6) Non-spiral galaxies. How do they end up in equilibrium? What difference is critical to making the spiral shape?

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Originally Posted by Shaula
I can see a number of questions that I would like to see modelled.

1) Star formation. Unless you trigger it at fixed locations the spiral won't form. Take your diagram and add in a few hundred other particles that start at random locations on the disk edge. No spiral will form.
2) Angular momentum. Why are these objects shedding it? How is it lost? When things are ejected from the core perpendicularly how do they somehow change their vectors enough to get recycled into the edge of the disk?
3) AGNs are not always on. Sporadic ejections of matter, even if you can get around the recycling issue above, won't result in the smooth distribution of dark matter needed.
4) Bars. How do they fit into your model?
5) Age distribution. We see the oldest stars near the centre - if whole stars are recycled shouldn't see more very old stars at the edges? If we ignore stars and just look at the gas - we see a metallicity gradient running to the core. I.e. more metals nearer the core. Why, if this gas is being recycled? Does this gradient limit the rate of recycling consistent with it?
6) Non-spiral galaxies. How do they end up in equilibrium? What difference is critical to making the spiral shape?
First things that come to mind are:

1) all of the hundred particles would follow a spiral pattern, why some 'light up' and we are lucky enough to see what's happening, might be to do with how the dark matter is landing on the disc edge as a filament 'igniting' a region, which then spirals in.

2) Good question, mentioned by Ken G in Q&A. The lost angular momentum of an object spiralling in, would be turned to angular momentum of the object (spinning) or somehow transferred to the galaxy as a whole. There might be some resistance to the tangential component to slow it down.

3) AGNs doing periodic outbursts could account for where the incoming matter goes. The smooth distribution you mentioned is due to the constant radial speed of incoming matter. This matter might come from AGNs from the original galaxy and also from the outbursts from all other galaxies.

4) Not sure, might be answered later.

5) Old stars near the centre fits the model ok. The stars might usually be formed at the edges and spiral in over approx. a billion years or maybe longer. Most objects reaching the centre would collide with others and be destroyed, becoming the dark matter. Metallicity - later.

6) This ATM model is about spiral galaxies.
Last edited by john hunter; 2018-Jun-28 at 11:31 PM.

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Originally Posted by john hunter
1) all of the hundred particles would follow a spiral pattern, why some 'light up' and we are lucky enough to see what's happening, might be to do with how the dark matter is landing on the disc edge as a filament 'igniting' a region, which then spirals in.
OK, but that contradicts observations. We can map starburst regions and they do not happen at the edge of a galaxy. They happen along spiral arms (which are visible due to the large, short lived stars in them). So either your infalling filament somehow ignites star formation along its entire inspiral or something is seriously wrong with our understanding of stellar lifetimes. Also - the dark matter halo is huge compared to the galaxy. Why does this starburst only happen inside a magic radius to make the galaxy? Why doesn't it happen a long way out?

Originally Posted by john hunter
2) Good question, mentioned by Ken G in Q&A. The lost angular momentum of an object spiralling in, would be turned to angular momentum of the object (spinning) or somehow transferred to the galaxy as a whole. There might be some resistance to the tangential component to slow it down.
So a key prediction of yours in the first case would be an increasing spin rate for objects as you go into the galaxy. Could you please run the numbers? How much faster would you expect the Sun to be spinning when it reaches the core? How much slower would you expect it to be spinning a the rim? I suspect the numbers will be below detection thresholds but it would be nice to see that. The other fixes are ... problematic. They require a host of unknown effects to shift angular momentum around in a very specific way. They make dark energy look like an elegant and justified-from-first-principles fix.

Originally Posted by john hunter
3) AGNs doing periodic outbursts could account for where the incoming matter goes. The smooth distribution you mentioned is due to the constant radial speed of incoming matter. This matter might come from AGNs from the original galaxy and also from the outbursts from all other galaxies.
But if the matter is ejected by the AGN and then comes back around to replenish the disk (you did say these systems were in a kind of equilibrium) what mechanism takes very clumpy, scattered ejecta and somehow smooths them out to form a roughly constant inflow to give us that smooth profile?

Originally Posted by john hunter
5) Old stars near the centre fits the model ok. The stars might usually be formed at the edges and spiral in over approx. a billion years or maybe longer. Most objects reaching the centre would collide with others and be destroyed, becoming the dark matter. Metallicity - later.
Ah, now we have an added issue. Dark matter doesn't behave like baryonic matter. How does your ejection mechanism stop it interacting via anything but gravity? If it doesn't then how does your ejected dark matter shed angular momentum and conserve mass without leaving a strong signal? Why doesn't it clump? And why can't we map it spectroscopically?

And for the last point - happy to exclude things outside the scope of the idea. I'll stop asking about other galaxy types.

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Shaula:

About 1) Since starbursts happen in denser regions, something has happened to create the dense region in a spiral shape. Starbursts then occur all along this dense region.
Spiral arms tend to occur in pairs opposite each other. This could be due to matter ejected from the nucleus causing 4 filaments going out of the core perpendicular to the disc (AGN), going in a loop shape returning to the disc at your magic radius, a pair on each side and meeting again in pairs, on the disc, one from above and one from below. The filaments could last a long time continually creating a dense region at the magic radius which has spiralled in towards the centre.

2) The spinning would have to be very fast, so transfer of angular momentum to the rest of the galaxy is preferable. It might not need a complicated fix, perhaps just a kind of drag effect tangentially.

3) The smooth profile: You mentioned the dark matter halo being much bigger than the 'magic radius'. The halo would be due to ejections from all other galaxies merging over a long time and giving a kind of constant density in the universe which is know to be approx. the critical density (3H^2/(8*pi*G)). The halo has density profile rho(r)=v^2/(4*pi*G*r^2), where v is the constant tangential velocity, typically 10^5. So the halo would gradually reduce in density (with radius) until it matches the critical density of the rest of the universe, at r = (v/c)R where R is the Hubble radius (c/H). It is this in-falling halo which gives the smooth profile.

5) Not enough is known about dark matter yet, but perhaps it is dynamic, forming the halo, travelling at constant speed to the centre of galaxies, being ejected, some returning to the same galaxy, some being attracted to other galaxies becoming part of their halos, etc... a continuous dynamic process.
Last edited by john hunter; 2018-Jun-29 at 09:05 AM.

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OK, I am finding this idea less and less attractive now. I thought at first that you had a 'simpler' explanation for rotation curves and spiral galaxies but it looks like your ideas require a large amount of poorly defined mechanisms to make them even conceptually plausible.

If starbursts are triggered along a spiral path by this unknown mechanism then there is no need for your radial inflow. If they do not happen along a spiral path then your ideas contradict observations. These filaments are also problematic as there is no obvious way for them to form, evolve and return while remaining largely invisible.

If the spin is so fast then you require either matter which doesn't conserve angular momentum or another unknown mechanism or set of interactions to fix the kinematic problems with the radial inflow.

The 'smooth halo' requires another poorly defined mechanism to smooth out clumpy ejecta from the AGN, you also need some other unknown interaction to smooth the dark matter on realistic timeframes without it being modified so much it clumps. There is a lot of ad hockery required here.

Overall an interesting idea but one which requires a lot of patches to fix issues with basic physics and observations. These patches then destroy the only real attractive property of the idea - its simplicity. I can't see that it is particularly likely or something I'd be motivated to pursue on aesthetic grounds.

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Originally Posted by Shaula
If starbursts are triggered along a spiral path by this unknown mechanism then there is no need for your radial inflow. If they do not happen along a spiral path then your ideas contradict observations.
The radial inflow takes the denser region inwards in the spiral pattern. The denser regions being formed at two points on the disc opposite each other. But not at one quick instance of time - the denser region is created for an extended period of time but at the same points on the disc. So as matter is arriving at the disc, matter that had arrived, say a million years before, has been swept further towards the centre.

So that's an idea how the spiral dense region is formed, where the conditions are better for star formation.

There may be other reasons why the dense region forms, but it might be a way for us to see the true motion of matter in a galaxy.

You are right to point out questions that need dealing with, it's going to need time to look into them.

----------------

A constant radial speed (with radius), as well as a constant tangential speed can:

1) Mean that matter would move inwards towards the centre in a spiral pattern.

2) Give the right density profile which leads to a constant m(r)/r for each value of r and hence the flat rotation curves. There is no good and simple explanation of why the m(r)/r is constant. If you know of one, please describe it or is there a link?
Last edited by john hunter; 2018-Jun-29 at 07:44 PM.

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Originally Posted by john hunter
A constant radial speed (with radius), as well as a constant tangential speed can:
1) Mean that matter would move inwards towards the centre in a spiral pattern.
Density waves can and do explain this already and have the advantage that they appear pretty much spontaneously in simulations and replicate what we see pretty well. Unless your ideas can be shown to produce better results or can generate a testable prediction that tells the two apart then there is no advantage (because they introduce an arbitrary new complication - the radial inflow). Your ideas also need developing in the areas of messy spirals such as NGC 7098 or loosely wound spirals such as M106.

Originally Posted by john hunter
2) Give the right density profile which leads to a constant m(r)/r for each value of r and hence the flat rotation curves. There is no good and simple explanation of why the m(r)/r is constant. If you know of one, please describe it or is there a link?
There is a good and very simple explanation of why DM halos have the form they do. It is the form you would expect dark matter which only interacts gravitationally to have. That was why I mentioned the NFW and pseudo-isothermal profiles in my earlier reply to you. They are not fitted, they are derived from the basic expected properties of DM. Have a read around on them - Wikipedia has some relevant references. The Millenium simulation is also worth a look - it generated DM halos from first principles. And they were close to what we observe (I'm not going to say they were perfect, but they were tolerable)

So I stand by my earlier comments. Unless your ideas can be shown to match observations better than the current models then I don't see them offering any advantages. They are more complex and have more arbitrary fixes / interactions in than the current models. They don't appear to be compatible with observations without several fixes or assumptions I don't see as physically justified. Unless they can be demonstrated to outperform current models there really isn't any compelling reason to adopt them. You are, as ever, welcome to prove me wrong!

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OK, this paper was interesting https://arxiv.org/abs/1005.0411 Equations (24) to (29) gives the formulae for different profiles.
It’s fine to try and fit a formula to the shape of the rotation curve, and the more complicated you are willing to make it, the closer the fit that can be obtained. But there is no understanding from this kind of thing about the mechanism which leads to the flat part of the rotation curves.

Wikipedia has this on the Millennium simulation - https://en.wikipedia.org/wiki/Millennium_Run in the paragraph near the beginning which starts… Since…
“In addition to improving the treatment of the astrophysics of galaxy formation, recent versions have adjusted the parameters of the underlying cosmological model to reflect changing ideas about their precise values.”

There are six adjustable parameters for the LCDM model, which have changed to help it match observations. The Millenium simulation no doubt has a few more. There could be an almost unconscious confirmation bias, with programmers thinking they’ve got some bug or error in the program, if it didn’t produce results matching observations. After hundreds of adjustments until it matches, they are then pleased with it and it’s then published.

The ATM proposal is a new idea and it’s not really justified to accuse it of having fixes or assumptions, which were in any case, just suggestions to describe the kind of activity which has somehow revealed the type of in-falling that could be occurring. Especially so when the models you have mentioned probably match observations, but with many parameters and 20 years of adjusting by thousands of scientists. Also with still no understanding of e.g. dark energy which is a major component of the model.

As for the galaxies you mentioned: In polar co-ordinates the angle theta =[v(t)/v(r)]*ln(r(0)/r) ….... r(0) is a starting radius, v(t) and v(r) the constant tangential and radial speeds respectively. If v(t)=2v(r), it’s about 80 degrees before the radius halves each time. If v(t)=9v(r), it’s 360 degrees before the radius halves, i.e a loosely bound spiral.
Last edited by john hunter; 2018-Jun-30 at 08:05 AM.

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The power (luminosity) that needs to be generated by an AGN is typically 10^38W and can be as high as 10^41W.

Accretion onto a black hole is a problematic mechanism to generate it (in mainstream theory) for a couple of reasons:

1) The Black hole itself is an object with a singularity, a place of infinite density and pressure, things which are not normally accepted in other areas of physics.

2) The efficiency of turning matter into radiation energy , used in the models, is very high approx 50%....and what happens to baryon conservation number? The models seem to apply E=mc^2 and bingo, there is your required energy.

With the spiralling in model: There is a mass within radius r of m(r) = (v^2/G)*r where v is the tangential velocity v(t)

In one second the mass within radius v falls into the centre and is ejected. Not necessarily smoothly, sometimes as sudden jets, but on average there is (v^3/G) kg/s being ejected. With a typical v being 2x10^5, and using E=mc^2 it is up to 10^43W.

The efficiency of nuclear fusion is approx. 0.7%. Without using the high efficiency of 50% above the values of 10^38W or 10^41W can be achieved as luminosity values, with most of the energy ejected still being in mass form.
Last edited by john hunter; 2018-Jun-30 at 08:26 AM.

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Originally Posted by john hunter
OK, this paper was interesting https://arxiv.org/abs/1005.0411 Equations (24) to (29) gives the formulae for different profiles.
It’s fine to try and fit a formula to the shape of the rotation curve, and the more complicated you are willing to make it, the closer the fit that can be obtained. But there is no understanding from this kind of thing about the mechanism which leads to the flat part of the rotation curves.
No idea why you have used that paper - as I told you the Wikipedia article (or just a more directed search) links back to the original paper. https://arxiv.org/abs/astro-ph/9508025

It clearly provides the theoretical reasoning behind the profile that came to be known as the NFW profile. The parameters in it (just the two - scale radius and initial density) adjust to fit the wide range of galaxies we see. So. There you go. As I said, a theoretically justified curve which explains the flat nature of the curve and has only two parameters.

So how about you drop the claim that your ideas have greater powers of explanation than the mainstream and focus on showing that they result in better predictions?

Originally Posted by john hunter
There are six adjustable parameters for the LCDM model, which have changed to help it match observations. The Millenium simulation no doubt has a few more. There could be an almost unconscious confirmation bias, with programmers thinking they’ve got some bug or error in the program, if it didn’t produce results matching observations. After hundreds of adjustments until it matches, they are then pleased with it and it’s then published.
They did not vary the cosmological parameters to make the simulation work. The six parameters were probed using a range of observational tests independent of the simulation. The point is that these parameters, derived from independent experiments, yielded recognisable DM halos. To write off their work as just someone tweaking a few constants until it matches our expectations is, frankly, insulting to the whole modelling and simulation community.

Originally Posted by john hunter
The ATM proposal is a new idea and it’s not really justified to accuse it of having fixes or assumptions, which were in any case, just suggestions to describe the kind of activity which has somehow revealed the type of in-falling that could be occurring. Especially so when the models you have mentioned probably match observations, but with many parameters and 20 years of adjusting by thousands of scientists. Also with still no understanding of e.g. dark energy which is a major component of the model.
It is perfectly justified to point at fixes that make the idea more complex and have little theoretical justification. You have several huge gaps in the idea that you are papering over. The dark matter hypothesis has really only got one big fix in it - matter which only interacts gravitationally. The rest is standard physics. Dark energy is not relevant in this case as you have already restricted the scope of this idea to spiral galaxies and their internal kinematics. You can't have it both ways. Meanwhile your idea has at least three or four big, serious, possibly new physics patches it requires just to get it to conceptually work. I fully expect you will need more to make it work analytically. These may turn out to be justified. If the resulting model performs better. But at the moment even the concept is more complex and less rooted in standard physics than DM. Oh, and it still needs DM.

Is your idea at the stage where you can provide any detailed calculations for it? Things like the structure of the ejecta halo, required density of the invisible filaments, the metalicity gradients you mentioned. Are there any areas of the idea you feel are sufficiently advanced to study in more detail? I am trying to be fair, here, and give you an area we can get into more depth on. At the moment the concepts are not convincing, so now is the time to see if all the extra additional galactic mechanisms you need are worth the headache of introducing.

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It's probably best to slow down the defence of the proposal for a while. That's not to say the idea is wrong, but it's not developed enough and needs time to develop.

Not sure if the filaments idea was correct, but there are still two main advantages of a constant inwards radial speed - giving the right density profile for the constant tangential speed and the spiral pattern.

There were no insults to any mainstream scientists who do a fantastic job. But confirmation bias can happen almost subconsciously and it's important for others to scrutinise mainstream cosmology/physics and try and find improvements.

Here is a picture of lobes https://nasaviz.gsfc.nasa.gov/10918 that the mainstream model might find hard to account for. They certainly need a great deal of matter/energy being emitted from the nucleus. Perhaps the v^3/G rate of emission, discussed in post 19 might help.
Last edited by john hunter; 2018-Jul-01 at 09:43 AM.

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Originally Posted by john hunter
Here is a picture of lobes https://nasaviz.gsfc.nasa.gov/10918 that the mainstream model might find hard to account for. They certainly need a great deal of matter/energy being emitted from the nucleus. Perhaps the v^3/G rate of emission, discussed in post 19 might help.
The current model for that has been around since the mid 70s. It has had a few refinements but otherwise works fairly well. So the mainstream doesn't really have an issue with these structures - we see them in other galaxies and we see them forming associated with jets. So a period of activity for our galaxy fits the observations.

Good luck developing your ideas further, will see what you come back with.

23. Originally Posted by john hunter
It's probably best to slow down the defence of the proposal for a while.

[...]

That's not likely to work out the way you want it to. If this thread remains open, you will be expected to follow our rules answer the questions put to you. You risk infraction if you do not. You can ask (via report) for the thread to be closed without penalty and later ask for it to be reopened, so long as it's prior to its 30-day time limit. Just remember: this is your one shot with this idea in the ATM forum.

In the future, ensure your claims are at least moderately defensible. The ATM forum is not intended for speculation or spit-balling.

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Originally Posted by john hunter
The power (luminosity) that needs to be generated by an AGN is typically 10^38W and can be as high as 10^41W.)
I watched a program on Sky TV last night about quasars. I'm sorry, I don't have the details to hand. But Phil Plait was one of the commentators. It may have been this: How the Universe works, the quasar enigma. The program said there was an inflow into the central supermassive black hole. This sounds reasonable to me in that when the solar system formed, there was an inflow that ended up forming the Sun. However the Earth isn't spiralling into the Sun, and in similar vein I wouldn't expect the Sun to be spiralling in towards Sagittarius A*.

Originally Posted by john hunter
Accretion onto a black hole is a problematic mechanism to generate it (in mainstream theory) for a couple of reasons:

1) The Black hole itself is an object with a singularity, a place of infinite density and pressure, things which are not normally accepted in other areas of physics..
I'm confident that a black hole isn't a place of infinite density and pressure. That's a hypothesis that's grown out of Hawking and Penrose singularity theorems, and has gained credence over the years. However it contradicts Einstein's general relativity.

Originally Posted by john hunter
2) The efficiency of turning matter into radiation energy , used in the models, is very high approx 50%....and what happens to baryon conservation number? The models seem to apply E=mc^2 and bingo, there is your required energy.
I'm also confident that the claims that the AGN is powered by matter reaching a high temperature in the accretion disk, as per the program I saw last night, are also wrong.

25. I have no inclination to take john hunter's idea seriously because it is at odds with mainstream theory and nobody has shown observations of stars systematically spiraling in. I cannot see any reason for publishing a paper proclaiming that such motion is conclusively ruled out, since I have no reason to expect it. John's interpretation of the feedback in the other thread as justifying the consideration of such a possibility is contrary to my way of thinking. Such motion should be relatively easy to detect in large nearby galaxies such as M31, if it occurs.

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Originally Posted by The Physics Detective
I watched a program on Sky TV last night...The program said there was an inflow into the central supermassive black hole.
Thanks, The Physics Detective.

This paper https://arxiv.org/abs/1006.0064 page 105 says "Gas is streaming into the central parsecs... [of the Milky Way] ...at a substantial rate" start of 3rd paragraph of Concluding Remarks.

Also some papers have now been found showing a radial velocity dispersion at the centre of the Milky Way:

https://arxiv.org/abs/0803.1826 "Radial Velocities of Stars in the Galactic Center" shows a velocity dispersion of 113km/s - table 5 and 6, pages 59 and 60 and in the summary page 27 is... "The measured velocity...exceed the maximum values allowed by circular motions...suggesting that these stars move in high eccentricity orbits".

https://arxiv.org/abs/1805.00275 "The central velocity dispersion of the Mily Way bulge" shows a radial velocity dispersion of 140 km/s, Figs 1 and 10, pages 2 and 7.

As the ATM proposal is that there is a constant inward radial speed (of similar magnitude to the tangential) in the region where the tangential rotation curve is flat - all this matter has to go somewhere.

The papers above show a radial velocity dispersion of about the same size at the centre. (The earths tangential speed is approx. 230 km/s).

It could well be that, instead of orbiting, stars near the centre are zooming in towards the central black hole, usually missing and moving outwards again, but occasionally getting too close and being 'eaten' or absorbed by the black hole.

By considering the flat region of the rotation curve, the inward flow is of order v^3/G, (post 19) - approx. 10^26 kg/s or 1000 solar masses per year. A Galactic nucleus contains millions of stars in a relatively small volume. So it needs 1000 such stars to be absorbed by the central black hole per year, to maintain a stable continuous situation. Matter being periodically ejected perpendicular to the disc.
Last edited by john hunter; 2018-Jul-03 at 09:29 AM.

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Originally Posted by john hunter
This paper https://arxiv.org/abs/1006.0064 page 105 says "Gas is streaming into the central parsecs... [of the Milky Way] ...at a substantial rate" start of 3rd paragraph of Concluding Remarks.
I see it. Genzel Eisenhauer and Gillessen are well respected astronomers.

Originally Posted by john hunter
Also some papers have now been found showing a radial velocity dispersion at the centre of the Milky Way: https://arxiv.org/abs/0803.1826 "Radial Velocities of Stars in the Galactic Center" shows a velocity dispersion of 113km/s - table 5 and 6, pages 59 and 60 and in the summary page 27 is... "The measured velocity...exceed the maximum values allowed by circular motions...suggesting that these stars move in high eccentricity orbits".
I think everybody is happy with that too. We've all seen the various gifs. Here's one from Stephan Gillissen's home page: http://www.mpe.mpg.de/~ste/data/e.gif

Originally Posted by john hunter
As the ATM proposal is that there is a constant inward radial speed (of similar magnitude to the tangential) in the region where the tangential rotation curve is flat - all this matter has to go somewhere.
The trouble is that "but the accretion into the event horizon at the present time is orders of magnitude lower than simple theoretical estimates had predicted". So IMHO your ATM proposal is a step too far.

Originally Posted by john hunter
It could well be that, instead of orbiting, stars near the centre are zooming in towards the central black hole, usually missing and moving outwards again, but occasionally getting too close and being 'eaten' or absorbed by the black hole.
From what I've seen, I think that is the case.

Originally Posted by john hunter
By considering the flat region of the rotation curve, the inward flow is of order v^3/G, (post 19) - approx. 10^26 kg/s or 1000 solar masses per year. A Galactic nucleus contains millions of stars in a relatively small volume. So it needs 1000 such stars to be absorbed by the central black hole per year, to maintain a stable continuous situation. Matter being periodically ejected perpendicular to the disc.
Trust me John, if 1000 stars were going into that central black hole every year, we'd know about it. See the 2013 AMPS paper an apologia for firewalls. Take a look at the conclusion, see footnote 31 on page 27, and check out reference 87. I rather think there are better topics for an ATM proposal here.

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So the model suggests a steady inward speed vr similar to vt, in the flat region, giving an inwards motion of matter of vt^2*vr/G kg/s. In the flat region the density is rho(flat) = vt^2/(4*pi*G*r^2), caused by the steady inflow.

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.

The inwards speed inside the bulge isn't vr for each object, as in the flat region. Instead there are millions of stars in random 3D elliptical orbits - giving an almost constant density in the bulge of rho(bulge)=3v^2/(4*pi*G*rv^2) three times the density of the flat region at rv

There is an average inward motion of matter in the bulge due to approx. 1000 stars per year joining the CMO (Central Massive Object), not necessarily a black hole. These stars are replaced in the bulge from the flat part of the disc and the same amount is ejected (on average, but in bursts), as jets of AGN.

Originally Posted by The Physics Detective
Trust me John, if 1000 stars were going into that central black hole every year, we'd know about it.
The black hole accretion proposal is approx. 50% efficient but violates baryon number, and black holes have singularities, so instead it is proposed that radiation is produced at nuclear efficiency levels of 0.7 %. The pressure build up from the incoming matter causes occasional sudden 'escapes' of matter and radiation perpendicular to the disc.

Perhaps you have seen this for a pan of water with a heavy lid or plate on it, when boiled by heating, Occasionally the lid is lifted allowing a short, sudden escape.
Also a 'Jif' Lemon analogy. It's a plastic lemon which can be filled with water and has a tiny hole, originally for squirting out the lemon juice. Good for kids water fights! Only a slight pressure around the lemon causes a very fast, very narrow jet of water to be pushed out.
Last edited by john hunter; 2018-Jul-04 at 10:17 PM.

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Originally Posted by john hunter
The stars in a spiral galaxy are moving at approximately constant radial speed towards the galactic nucleus.
Difficult to defend because of the physics that says that this may be wrong.
A star is basically in orbit around the mass that is inside its radius with an influence from the mass outside of its radius. A guess would be that any speed would be out from the galactic nucleus. An analogy would be the Earth around the Sun being tugged on by maybe 100 Jupiters. The Earth should move outward to a new stable orbit.

More importantly, 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.

ETA2: Some of the difficulty above could be removed by the answer to the following question:
IF01: Please find radial velocities of stars that are directly outward from the Sun or directly inward, john hunter.
Those stars will have a radial velocity that is directed toward or from the galactic center. If they are not what your ATM idea predicts then it is wrong.
Last edited by Reality Check; 2018-Jul-05 at 03:22 AM.

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Originally Posted by john hunter
Each object in the galaxy would reach the centre and be ejected perpendicular to the disc.
How do the stars get ejected when there is the mass of the central bulge to hold them back and even the supermassive black hole to eat them?

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