Dark Matter

[Jay-qu]

The merit of those papers is determined by the veracity of their mathematics and empirical analysis, not by whether they are acceptable to a community dominated by the Dark Unseeable Matter Bunch and Milgrom's Mondiots. The essential point raised by those papers is that the Newtonian weak field approximation is the wrong approach to analysis of stellar velocities within galaxies and galactic velocities within clusters. The onus is now on those who subscribe to DM, or to MOND, or indeed to any other patch-up, to prove that the Newtonian weak field approximation is valid in those aforementioned cases. If they cannot do so then perhaps they should accept that Cooperstock et al have shown Einstein's GR has another piece of supportive evidence, viz the correct prediction of galactic rotation curves and galactic velocities within clusters.

 

The veracity of their maths is one of the things the peer review process is supposed to check. I cannot vouch for whoever reviewed these papers as I am not an expert in GR, but I can say that something must be going wrong somewhere. GR also predicts DM through the observations of gravitational lensing, I dont think there is an easy way to reconcile these two observations. If we accept that GR is a consistent theory of gravity, then one of the observations must be wrong. Now considering the case of the bullet cluster, it makes it considerably less likely that lensing observations are wrong.

[CraigD]

I read through this article (Galactic Dynamics via General Relativity: A Compilation and New Developments (arxiv:astro-ph/0610370)) …

 

But it was from 2006 and the last one you linked is from 2007. Any idea of the follow ups?

The last paper cruel2Bkind linked, "General relativistic dynamics applied to the rotation curves of galaxies" by J. D. Carrick and F. I. Cooperstock, is from 2011/01/18.

 

Cooperstock also has a book which appears to explain his approach in greater depth and to a more general audience, "General Relativistic Dynamics: extending Einstein's legacy throughout the universe". It’s introduction can be read for free, and has me nearly enticed me to get and read the whole book, even in hardpapercopy if necessary.

 

The merit of those papers is determined by the veracity of their mathematics and empirical analysis, not by whether they are acceptable to a community dominated by the Dark Unseeable Matter Bunch and Milgrom's Mondiots.

The merits of an idea are most certainly not determined by the rhetoric of name-calling – don’t do that, c2Bk!

 

… then perhaps they should accept that Cooperstock et al have shown Einstein's GR has another piece of supportive evidence, viz the correct prediction of galactic rotation curves and galactic velocities within clusters.

I don’t believe there’s widespread acceptance that Cooperstock et al have correctly predicted the galactic rotation using realistic physical assumption and GR. For example, Mikolaj Korzynski’s 2005/10/29 paper "Singular disk of matter in the Cooperstock–Tieu galaxy model" asserts that the galactic model presented in Cooperstock & Tieu’s 2005/07/26 "General Relativity Resolves Galactic Rotation Without Exotic Dark Matter" “posseses an additional

source of gravitational field in the form of a rotating flat disk at z = 0”, so is unphysical.

 

GR also predicts DM through the observations of gravitational lensing, I dont think there is an easy way to reconcile these two observations. If we accept that GR is a consistent theory of gravity, then one of the observations must be wrong. Now considering the case of the bullet cluster, it makes it considerably less likely that lensing observations are wrong.

Cooperstock et al’s appear to me to be not attempting to explain every observation, but suggesting that, with sufficient application of GR, explanations can be found without assuming the existence of dark matter, and encouraging physicists to pursue them.

 

He points out that GR explanations are the accepted consensus for the largest scale of the universe as a whole (and I’ll add, the scale of solar systems, eg: the prediction of the correct precession of Mercury’s orbit), but not for the scale of galaxies and clusters of galaxies, a consensus he calls “a bizarre view”.

 

Interestingly, from the intro to his book above, Cooperstock promises to argue that the acceleration of expansion, vis-à-vis the cosmological constant, requires exotic matter, so he’s not simply denying the existence of dark matter on the ground of there being no direct observation or material science explanation of it.

 

In short, I think Cooperstock is more of a theoretical strategist than footsoldier - which is sensible, IMHO, as big modern physic questions are usually way more than a single theorist or team of theorists can handle alone. I’m very glad to learn of his work, and give a big thank you to cruel2Bkind for the introduction. :thumbs_up

[athinker]

Here's the problem I have with the invocation of dark matter to explain the galactic rotation curve.

 

First I want to dispose of this colliding galaxy issue.

 

Galaxies don't collide with electromagnetic interactions. There may be a few such collisions but the distances between stars and gas is so great that most of the collision interaction is gravitational. Dark matter should stay with the galaxy interacting gravitationaly same as normal matter. It wouldn't go flying off in one direction like the load on a truck in collision. Trucks in collision is an electromagnetic interaction.

 

The rotation curve anomaly.

 

The issue here seems to be one of visible matter to mass/rotation ratio.

 

The solar system rotates nearly exactly according to Newton because most of the mass is in the sun. The sun is visible for the obvious reason of its luminosity. We have a ratio of mass/luminosity/planetary rotation.

 

The rotation anomaly problem presents as follows; The mass/luminosity/stellar rotation of the core stars match Newton. The stars in the disk and outskirts don't match.

 

The mass in the disk is less luminous therefore less visible than mass in the core. the mass is there just not visible. This dark matter is invoked to explain this.

 

I disagree with this explanation for the following reaasons;

 

There is a logical question that must be asked. Dark matter is...darker than what? Darker than the matter that rotates according to Newton, core matter. That's the matter it's being compared to.

 

Seems the way to solve the problem without invoking matter with unknown physical properties is to examine the physical properties of the matter we do know.

 

Why is matter luminant? It emits light through fusion and reflects light from nearby fusioning stars.

 

What do we know about fusion? Fusion in stars takes a lot of matter to happen. Don't have enough matter it doesn't happen.

 

There's your clue right there.

 

What is it about the core regarding "lots of mass" that doesn't exist in the disk and outskirts? Well the core has "lots of mass" and the disk and outskirts don't. One should expect the mass to fusion ratio of the core to be greater than the disk. It should have a higher mass to luminance ratio than the disk. This is what we see. This is the galactic rotation anomaly in a nutshell.

 

So rather than invoking some supernatural material, force or being in the disk to solve the problem (that's real old fasioned) why not invoke more fusion to mass in the core as an elegant and calculable solution?

 

 

Considering the above I would like to do some calculations. I may be able to produce a new tool for cosmology.

 

To do the calculations I need a star catalog with the following information.

 

A free online star catalog in ASCII format (not pdf) containing a large number of stars in our galaxy, selection of stars from the core to the outskirts of the disk. the rotation speeds of the stars relative to a "fixed" referance frame, say some distant quasars, the distances of the stars from the centers of their rotations.

 

Any astronomers here that know of such a catalog?

 

I think I can make a script to do a large number of calculations. I want to calculate the density to luminosity ratio of various parts of the galaxy to see if there is a universal consistancy to it.

[JMJones0424]

Welcome to Hypography, athinker.

 

I think you are mistaken. The "dark" in dark matter does not mean matter which does not emit visible light. What you seem to be describing is the intestellar medium, and the mass of this baryonic matter that is not emitting light is accounted for in the models. Dark matter is not "darker than" baryonic matter, it is matter that is incapable of emitting or reflecting eletromagnetic radiation of any kind.

[athinker]

Hi JMJones0424.

 

Thanks for the welcome.

 

 

When I wrote "luminosity" and "visibility" I meant all detectable non gravitational effects.

 

Is "there are less detectable non gravitational effects in the disk than in the core" a fair description of the issue?

 

Put another way "There is less electromagnetic radiation to mass detected in the disk than there is detected in the core."

 

Mass that is being orbited as reflected in the speed to distance ratio, as defined by Newton, of the orbiting object .

 

Put my way "There is more radiation to mass detected in the core than there is detected in the disk."

 

Is that not a true statement?

 

Equaly true is the statement "dark matter is non fusioning matter". Yes?

 

Equaly true is the statement "Non existant dark matter or any other kind of non existant matter is non fusioning matter". Non existant matter is also non luminant.

 

By the way, How about that star catalog? Any ideas?

[Time_Travel]

Are there any observed(measured) scientific evidences for dark matter that they exist?

Is invoking the Dark Matter just to explain the rotation of the stars at the edge of galaxy a good scientific idea?

[athinker]

Are there any observed(measured) scientific evidences for dark matter that they exist?

Is invoking the Dark Matter just to explain the rotation of the stars at the edge of galaxy a good scientific idea?

 

Maybe, If it's understood as a placeholder for an unknown. As an unknown the placeholder indicates there is a mystery here. It can stimulate intrest and invoke some people to solve the mystery. What is unkown? Is it something we have never seen before? Or is it merely something overlooked in the interpretation of the observation.

 

In this case the unknown is the cause of a rotaional anomaly. It should stimulate you to look at all aspects of the observation and its interpretation.

 

In most cases in science and in everyday life mysteries are solved by looking more carefully at the interpretation of the observation. But often enough it's the observation that is at fault. In fact observation and interpretation are so closely linked that it can be hard to know where to look for the fault. With enough heads on the lookout we have substantial records of solving mysteries.

 

As far as your question about evidence for dark matter, Some might say the rotational anomaly itself alone is evidence. In my opinion that's circular reasoning. It is evidence of something. But not conclusivly existance of dark maatter.If, on the other hand, every other solution to the anomaly were shown to be wrong then that would add to the evidence. It wouldn't be conclusive unless it were proved that "every other solution" had been tried. More conclusive evidence would be if we could catch it in a bottle and play with it.

[joekgamer]

Isn't it called 'dark matter' because we can only observe it indirectly?

[athinker]

Isn't it called 'dark matter' because we can only observe it indirectly?

 

That's an intresting formulation of the question. It assumes there is an "it" there to be observed albeit indirectly. Also, Neptune was "observed" indirectly by its gravitational influence, mathematicly calculated, on the orbits of the other planets. It wasn't assumed to be dark matter. It was assumed to be something natural, an unseen planet, by the similarity of its gravitational effect on the other planets to the gravitational effect of the other planets on each other.

 

By making the correct assumption the correct the observational equipment was pointed in the correct direction and direct obsevation of it was made.

 

We could, and do, assume dark matter to exist and try to think of equipment and maths to make direct observation. But we mustn't overlook the possibility that some natural phenomena was overlooked in the interpretation of the observation. Possibly even a mundain and foolishly simple overlooked phenomena.

[joekgamer]

Neptune is a planet, so it is made of matter and therefore can be seen optically. Dark matter cannot. However, I was under the impression that it could be detected by its effects on other things (e.g. maybe it's opaque to EMR, or perhaps by the graviational irregularities it causes). Over time, it was figured out that a material with certain properties could cause these effects. Since this new material was seemingly undetecable, it was called 'dark matter'.

 

 

 

I could be wrong, though, so correct me if I am.

[CraigD]

(my PS note added)

Why is matter luminant? It emits light through fusion^{*see PS below} and reflects light from nearby fusioning stars.

This list of two – direct starlight, or reflected starlight – leaves out a third important way that ordinary atomic (baryonic) matter can be observed with electromagnetic radiation: by its absorption of starlight passing through it on its way to the observer. Technically, atomic matter can’t simply absorb light without reemitting it, but it can and does absorb specific frequencies of starlight and re-emit it in all directions and at lower frequencies, which to the observer is effectively the same as it the original light were destroyed.

 

A fourth way atomic matter can be observed is when it is heated enough to glow.

 

Because stars are collectively much larger and brighter than other glowing or reflective bodies, the vast majority of the light in the universe is from them. Nonetheless, we know a lot about atomic matter outside of start by how it absorbs starlight. That most of the universe is made of only a few simple molecules, nearly all of it the simplest, atomic hydrogen, and that we know precisely how hydrogen absorbs and emits light, makes these observations very informative.

 

Though the details are laborious and beyond my technical ability – I must trust the astrophysical community to know its subject – the scientific consensus is that observation doesn’t show, by a factor of about 4 times, enough atomic matter to account for the observed gravity-dominated motion of the stars, either moving within galaxies, or the collective motion of stars in galaxies relative to other galaxies.

 

The most popular hypotheses explaining this all share the assumption that about 80% of the mass in the visible universe is “dark” – can’t be detected in the usual ways ordinary atomic matter can be. They differ in specifically what this dark matter is.

 

In order of simplicity and familiarity, here’s my summary of the roster of dark matter candidates:

• Athinker gave the first one: dark matter is just ordinary atomic matter we can’t detect. I hope my explanation above is good enough to convince him and other readers to rule out these candidates.
   
  
• The next most obvious dark matter candidates are the usually particles of atomic matter – atomic nuclei (recall that most of the universe is hydrogen, so most nuclei are single protons) and electrons – but not bound into atoms. There are at least a couple of flaws with this hypothesis, so glaring that, to the best of my knowledge, I’m one of the few people to mention it, which I do only for completeness sake. These flaws can be summarized in two words: net charge.
  
  • First, because of the mutual attraction of particles with opposite charge, it’s practically impossible to keep a large number of them from forming atoms – that is, to keep them in a plasma state. Free electrons and protons in plasmas quickly combine, releasing photons (this is why plasma glows). Plasma can only be maintained by a steady influx of energy, which for a plasma massing 4 times the visible universe, would be gigantic. And, even if the plasma could be maintained, it would glow, so wouldn’t be dark, the key requirement of a dark matter candidate.
    
  • Second, even if a collection of protons and electrons massing 4 times the visible universe could be kept from combining into atoms – say through some incredibly organized orbits of the individual particles in which electrostatic and dynamic forces were kept in perfect balance the electromagnetic interaction is tremendously stronger – about 10³⁶ time¹ – stronger than the gravitational one. Instead of solving the somewhat subtle problems of galactic motion dark matter is meant to solve, huge collections of net charge would subject the ordinary mater universe to such gigantic forces it would rip it apart.
    

   

  [*]The next candidate is an ordinary nucleon with zero net charge – the neutron. Neutron’s aren’t stable – on average, free neutrons decay into proton electron pairs after about 15 minutes – but if enough ordinary matter is concentrated in one place – say the in the remains of collapsed stars under very specific conditions – a mass of about 1.5 to 2 solar masses of neutrons – a neutron star – is believed to be stable. So the dark matter could be a huge population of neutron stars

   

  A big problem with this is that every known neutron star is far from dark. Although in principle, a mass of pure neutronium (and likely even more exotic quarkium) wouldn’t interact with light the way ordinary atomic matter does, so would be “dark”, actual neutron stars appear to have ordinary matter “crusts” around their neutralism cores (not a major problem for their dark matter candidacy, as neutron stars are small, so even in vast numbers, might just be overlooked by observers), which are hot enough to emit in radio and x-ray frequencies (a big problem), and are often sounded by halos of ordinary matter or even companion stars that can crash onto their surfaces with huge energies, giving rise to some of the brightest x-ray sources in the sky: X-ray bursters - far from dark.

   

  If you could somehow “clean up and cool down” a population of neutron stars, they’d get my vote for dark matter – but short the intervention of super-technological universe-scale jokesters, I don’t see how this could possibly be done.

   

  [*]We now reach the first serious dark matter candidate, MACHOs, ordinary atomic matter objects that are simply small, dim, and hard-to-detect – quiescent black holes, ordinary (but quiet) neutron stars, brown dwarf and almost-dark white dwarf stars. These have been hunted for decades, though, and should have been found by now, so are pretty much ruled out.

   

  [*]Which leaves a class of candidates currently the favorite in the dark matter candidate race: weird, non-baryonic matter, the major ones being:

  • axions – hypothetical particles predicted by an unproven quantum mechanical theory but, despite several good experiments over the last 25 years, not yet observed.
    
  • neutrinos – either the well-known particle mass-dilated sufficiently that their slight known interactions with normal baryonic matter wouldn’t be noticeable, or a hypothetical kind of neutrino that doesn’t interact as much or at all other than gravitationally with baryonic matter
    
  • WIMPS – some particle similar to the above but even more hypothetical and unobserved, such as neutralinos.
    

Not a very pretty collection of candidates, which is why I find the dark matter problem so vexing, and alternative explanations, such as theoretical adjustments to the nature of space-time and gravity, such attractive alternatives.

 

A free online star catalog in ASCII format

...

Any astronomers here that know of such a catalog?

I’ve not claimed to be a “real astronomer” for over 30 years, but have you tried just googling “star catalog database”? The second find in that list directed me to the HYG database, the latest of which include about 120,000 stars in simple with simple geocentric positions and velocities (warning: use a real gunzip to decompress – my windows version, winrar, didn’t work)

 

PS: ^*The direct products of fusion, such as gama-ray photons from a proton-proton fusion reaction, are rarely observed, because they occur deep within stars, and are absorbed and re-emitted many times before escaping into space. Starlight is not “fusion light”, but rather the light of glowing gas in stars’ photospheres, and in lesser amounts, chromospheres, and coronas.

 

¹ see the wikipedia article fundamental interaction

[athinker]

Neptune is a planet, so it is made of matter and therefore can be seen optically. Dark matter cannot. However, I was under the impression that it could be detected by its effects on other things (e.g. maybe it's opaque to EMR, or perhaps by the graviational irregularities it causes). Over time, it was figured out that a material with certain properties could cause these effects. Since this new material was seemingly undetecable, it was called 'dark matter'.

 

 

 

I could be wrong, though, so correct me if I am.

Neptune has other properties that make it seen optically. It's large and it's nearby. However before it was confirmed opticly there were suggetions in the literature (published and careers based on them)that there may be a non Newtonian solution for the orbital anomaly just as there were suggestions for non Newtonian solutions for Mercury's orbital anomaly. The Neptunian solution was Newtonian The Mercury solution was not.

 

The only effect we are observing is the rotational anomally. There is no other. No EMR and no opacity to EMR. It's as if it's not even there. Just a rotational anomally. Some think that if dark matter exists it may be weakly interacting massive particles (WIMPs). But that is just a hope that there may be some non gravitational effect that may cause an observable, if weakly observable, phenomena. If WIMPs exist. But WIMPs are themselves only theoretical. So far no observables of dark matter as a solution in this case other than the rotational anomally itself.

 

There is also the possibility that other solutions are opposed and dismissed dishonestly to maintain interest in the mystery and funding for research into WIMPS, dark matter, Higgs bosons, etc.

[athinker]

CraigD,

 

With all due respect for the time you obviously put into your post. I find an "explanation" that hinges on an expression of confidence of "the astrophysical community to know its subject" to be unconvincing.

 

I find the astrophysical community's expressions of confidence in its ability to detect matter baryonicly at interstellar distances unconvincing in light of the fact that it balances its detection books by a fudge factor of 4 times by invoking dark matter. Less so in that I find nothing in the published literature on the Galactic Rotation Problem addressing the issue of a higher fusion to mass ratio in the core. Regardless of what detectables are under observation except for gravity they are all fundamentaly powered by fusion in stars. Well, except what powered the rotation to begin with. For that mater original heat from the creation would apply equally to all baryonic matter but would probably be slightly greater in the core due to insulating properties in the core.

 

That invocation of dark matter is used to solve other astrophysical mysteries is an unconvincing argument for invoking it in the Galactic rotation problem. Especially when the fusion issue is unadressed.

 

I guess we'll just have to disagree on that.

 

But have no fear. I have e-mailed the discoverer of the galactic rotation problem and asked her if she has considered the fusion issue. I doubt if she'll write me back but you never know.

[CraigD]

With all due respect for the time you obviously put into your post. I find an "explanation" that hinges on an expression of confidence of "the astrophysical community to know its subject" to be unconvincing.

Time permitting, I’ll try to research the observational astronomy details better. I was, briefly in 1977, a genuine professional observational astronomer (well, that might be stretching things a bit – I interned one summer at the Haystack observatory), so have at least a feel for the subject, though I was more of an instrument maker than a theoretician in those days.

 

The formalism of absorption spectra is fairly straightforward, so even an amateur like me can calculate the spectrum of an extragalactic light source assuming that the dark matter is a cloud of hydrogen.

 

A couple of question, athinker:

• I understand you are proposing a dark matter galactic halo made of non-ionized atomic (baryonic) matter. Am I correct?
  
• If so, I’m assuming this matter roughly matches the primordial abundance of elements is mostly hydrogen. Do you agree?
  

 

I find the astrophysical community's expressions of confidence in its ability to detect matter baryonicly at interstellar distances unconvincing in light of the fact that it balances its detection books by a fudge factor of 4 times by invoking dark matter.

I don’t understand what you’re saying here. The reason the astronomy mainstream consensus is that dark matter is not baryonic is because the mass necessary to explain galactic rotation, the orbital velocity of galaxies in clusters, and gravitational lensing is not in spite of this large, 4 times factor, but because of it. Were there not a dramatic discrepancy between observed the amount of visible mass and its motion, there would be no missing matter problem.

 

Less so in that I find nothing in the published literature on the Galactic Rotation Problem addressing the issue of a higher fusion to mass ratio in the core.

I don’t think you’re likely to find much literature involving the concept of a “fusion [rate?] to mass [of a large volume of space] ratio”, because the concept isn’t very useful.

 

The vast majority fusion reactions occur in the cores of stars, the vast majority of them the transmutation of hydrogen to helium, though the precise reaction path and intermediate and by-products of the reactions vary. The rate at which these reactions occur is determined primarily by the density of each star’s core, which is determined primarily by its total mass, and its age (since its formation). In principle, a star’s initial composition – primarily whether it is very poor in carbon abundance or not – is a factor, but the stars in the main disk-shaped part of a galaxy are similar in composition, so this factor is variable only when comparing very young, distant galaxies, to old, close ones.

 

The fusion rate is independent of average density of the star’s neighborhood – a star of given mass and age in a neighborhood with high average density, such as near the center of a galaxy, has the same fusion rate as one of the same mass and age in a low-density neighborhood, such as near its rim, or in a gap between spiral arms.

 

In short, stars don’t much care what’s outside of them. They shine as luminously when surrounded by nearly empty space, densely packed other stars, other massive bodies such as black holes, or, hypothetically, matter that can be observed only by its gravitational interaction, which is conventionally called “dark matter”.

 

In observing that few people write about the relationship between the density of a neighborhood in space and its rate of fusion, you’re doing something analogous to observing that few people write about the relationship between the mass of materials used to build houses in a neighborhood on Earth and its electricity consumption. The relationship is obvious – neighborhoods with many and/or big stars/houses tend to have lots of fusion/consume lots of electric energy – and the detailed cause so well understood it’s little remarkable, so not much written about.

 

But have no fear. I have e-mailed the discoverer of the galactic rotation problem and asked her if she has considered the fusion issue. I doubt if she'll write me back but you never know.

Athinker, do you mean you’ve sent an email to Louise Volders?!

 

Given that she published Neutral hydrogen in M 33 and M 101 in 1959, I imagine this person is now in her 70’s or older, and retired from professional/academic life, or dead.

 

Regardless, as best I can tell from her few later papers Volders was not much concerned with the astrophysical cause of the anomalies she observed 50+ years ago, so isn’t likely to be an authority on such research.

 

If you do learn anything about her, athinker, I’d enjoy reading about it here. My brief internet search turned up no biographical data on Volders. She (or perhaps he – I’ve found so little biography I can’t be sure) appears as only a name associated with a few papers. You’d be filling in a biographical void, providing a “where is she now?” note about an obscure by significant scientist.

[Jay-qu]

At this point I would just like to note that I am part of the scientific community researching dark matter and that I agree with everything Craig is saying. In lieu of the reputation system we used to have, I commend you here instead: Craig, your patience matched with your intelligence and fluid prose make you a formidably lucid explainer of all things scientific. I don't know where this site would be without you :thumbs_up

[athinker]

CraigD

 

Maybe the following picture will give you a better idea what I'm getting at. It is a mass distribution curve I calculated based on the "flat" rotational curve of the galaxy.

 

Point I want to make is where most of these rotational curve graphs in referance to a "galactic rotation problem" show a "predicted rotation" based on the mass distribution of the solar system. More than 99% of the mass is in the center. My mass distribution graph shows a comparison of galactic rotation curves to the solar system's rotation curve is absurd. Looks like a "rotational anomaly" when one compares things that shouldn't be compared as they are so different. It's like looking at an apple and saying there's something wrong with our basic understanding of physics because the apple doesn't resemble a cat.

 

Admitedly my graph is crude using as it does only 10 data points at 5,000 light year intervals. But it clearly shows that the mass of the galaxy is distributed roughly in the same pattern as most observational data such as xray emmission, infrared, and of course visible.

 

I'm working on a better graph using more data points based on actual star's rotation speeds. But it's slow going without having a star catalog with galactic rotation speeds listed. The one you mentioned as well as all others I've been finding are in a LINUX format that my machine won't read. Still working on it.

 

If you want to help I could use a list of stars at 1000 light year intervals from the center to the edge with their distance from center and their rotational speeds. 50 stars should do it. If you can extract the data from those catalogs. I'd even accept data of the location and rotational velocity of just clouds of dust and gas. Mass distribution data, rotational velocity data, distance from center data is very hard to find. Surprising as it's such basic data. Also surprising how many "astronomy/science" websites I'm running into that make excuses for not having the data.

 

PS

 

To be clear the "volumes" I'm talking about are not of a single star's, or even a few star's "neghborhood". I'm talking about "neighborhoods" of hundreds of thousands of cubic light years in volume. Even a volume of only 10 light years on a side is 1000 cubic light years in volume. It's not about how the density of mass in a volume affects the fusion that occurs in a given star in that volume. It's about how much of the mass in that volume gets into stars in the first place. If more of the mass gets in a star because the particles of mass in the volume are closer together then more of the mass is going to be fusioning.

[JMJones0424]

athinker- I hope you did not take my lack of replies to your posts as ignoring you, rather, I did not feel I had anything useful to add to the discussion. I am afraid that situation has not changed, but I want to go over a few of your posts to make sure I understand what you are saying, and maybe clear up a few misunderstandings of my own. This post is not meant to be authoritative. Instead, consider this entire post as a request for clarification from you and a request from me to everyone else to make sure I am not misunderstanding current theory.

 

... First I want to dispose of this colliding galaxy issue. Galaxies don't collide with electromagnetic interactions. There may be a few such collisions but the distances between stars and gas is so great that most of the collision interaction is gravitational. Dark matter should stay with the galaxy interacting gravitationaly same as normal matter. It wouldn't go flying off in one direction like the load on a truck in collision. Trucks in collision is an electromagnetic interaction.

 

In the previously referenced bullet cluster collision, the dark matter and the (my word) "accumulated" baryonic matter contained in stars are observed to go flying off specifically because they interact predominantly gravitationally. However, the interstellar gases, because they are more diffuse, do interact electromagnetically as well, and the gases slam into each other (figuratively) while the stars and dark matter go flying past each other. In your analogy, the interstellar gases are the trucks, and the "accumulated" baryonic mass in the stars and the non-baryonic dark matter are the load that goes flying past the point of collision. The reason that the bullet cluster collision is useful for illustration purposes is because we are able to observe the aggregation of the interstellar gases in the middle and the luminous stars that have flown out ahead of the gases. The interesting thing is that the effects of gravitational lensing do not match what we would expect if there was no dark matter. For one of the easiest to understand descriptions of the situation, please read this blog entry by "Planetary Astronomer Mike".

 

Now, when galaxy clusters collide, it's a bit like galaxies colliding. In this case, the galaxies themselves are sparse enough that they'll usually pass right through the other cluster unhindered. The ICM [intracluster medium], on the other hand will form a massive shock wave right in the center.

 

So, in the above picture there are a couple of combined observations. The red central area in the picture is an observation taken in X-rays, showing the massive quantities of hot, shocked ICM interacting. We also see on the left and right of this the two constituent groups of galaxies from either cluster which have passed through each other. The real clincher are the blue regions: according to the gravitational lensing of background galaxies produced by the interacting clusters, the blue regions are where most of the mass lies.

 

Thus, in spite of 90% of the visible matter being in the hot central red region, there's 10 times as much dark matter in the region of the galaxies themselves. Apparently, whatever this mysterious dark matter is, like the galaxies it too has the ability to pass straight through the other cluster unhindered.

 

The rotation curve anomaly.The issue here seems to be one of visible matter to mass/rotation ratio.The solar system rotates nearly exactly according to Newton because most of the mass is in the sun. The sun is visible for the obvious reason of its luminosity. We have a ratio of mass/luminosity/planetary rotation. The rotation anomaly problem presents as follows; The mass/luminosity/stellar rotation of the core stars match Newton. The stars in the disk and outskirts don't match. The mass in the disk is less luminous therefore less visible than mass in the core. the mass is there just not visible. This dark matter is invoked to explain this.I disagree with this explanation for the following reaasons;There is a logical question that must be asked. Dark matter is...darker than what? Darker than the matter that rotates according to Newton, core matter. That's the matter it's being compared to. Seems the way to solve the problem without invoking matter with unknown physical properties is to examine the physical properties of the matter we do know.Why is matter luminant? It emits light through fusion and reflects light from nearby fusioning stars. What do we know about fusion? Fusion in stars takes a lot of matter to happen. Don't have enough matter it doesn't happen. There's your clue right there. What is it about the core regarding "lots of mass" that doesn't exist in the disk and outskirts? Well the core has "lots of mass" and the disk and outskirts don't. One should expect the mass to fusion ratio of the core to be greater than the disk. It should have a higher mass to luminance ratio than the disk. This is what we see. This is the galactic rotation anomaly in a nutshell. So rather than invoking some supernatural material, force or being in the disk to solve the problem (that's real old fasioned) why not invoke more fusion to mass in the core as an elegant and calculable solution?

 

I still am not sure that I understand your position. We measure the rotational velocity of stars near the edge of spiral galaxies to be faster than expected given mass distribution that can be inferred through electromagnetic interactions. How does increasing the presumed mass at the core of the galaxy solve the problem? The rotational velocities we observe indicate more mass distributed throughout the galaxy, yet we have no other evidence of this missing mass existing other than its gravitational effects. It can not simply be interstellar gases, as this matter is already accounted for. It can not be missing mass at the core, as this would not solve the problem, but only exacerbate it (wouldn't it?).

 

Point I want to make is where most of these rotational curve graphs in referance to a "galactic rotation problem" show a "predicted rotation" based on the mass distribution of the solar system. More than 99% of the mass is in the center. My mass distribution graph shows a comparison of galactic rotation curves to the solar system's rotation curve is absurd. Looks like a "rotational anomaly" when one compares things that shouldn't be compared as they are so different.

 

I don't see any labels on your graph. If the x axis is distance from the core and y axis is mass, then your mass distribution curve would predict the same rotational problem that observations do not agree with, would it not? The orbital velocities of stars nearer the edge of the galaxy are far too fast given your mass distribution, thus the need for invoking dark matter. If your graph is supposed to represent something else, then I guess I didn't understand your explanation.