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Milky Way Dwarf Galaxies Thwart Newtonian Gravity?

11 May , 2009

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Here at Universe Today, the subject of Newtonian gravity always seems to lead to vigorous debate. Now, there’s new research to stoke it.

Manuel Metz, and astrophysicist at the German Aero-space Center, and his colleagues say dwarf galaxies in the Milky Way are arranged in a way that precludes the existence of dark matter — but also depends on it. 

“Maybe Newton was indeed wrong,” said Pavel Kroupa, an astronomer at Bonn University. “Although his theory does, in fact, describe the everyday effects of gravity on Earth, things we can see and measure, it is conceivable that we have completely failed to comprehend the actual physics underlying the force of gravity.”

As modern cosmologists rely more and more on the ominous “dark matter” to explain otherwise inexplicable observations, much effort has gone into the detection of this mysterious substance in the last two decades, yet no direct proof could be found that it actually exists. Even if it does exist, dark matter would be unable to reconcile all the current discrepancies between actual measurements and predictions based on theoretical models. Hence the number of physicists questioning the existence of dark matter has been increasing for some time now. Competing theories of gravitation have already been developed which are independent of this construction. Their only problem is that they conflict with Newton’s theory of gravitation.

In two new studies, Metz and his team have examined so-called “satellite galaxies.” This term is used for dwarf galaxy companions of the Milky Way, some of which contain only a few thousand stars. According to the best cosmological models, they exist presumably in hundreds around most of the major galaxies. Up to now, however, only 30 such satellites have been observed around the Milky Way, a discrepancy in numbers which is commonly attributed to the fact that the light emitted from the majority of satellite galaxies is so faint they remain invisible.

A detailed study of these stellar agglomerates has revealed some astonishing phenomena: “First of all, there is something unusual about their distribution,” Kroupa said, “the satellites should be uniformly arranged around their mother galaxy, but this is not what we found.” More precisely, all classical satellites of the Milky Way – the eleven brightest dwarf galaxies – lie more or less in the same plane, they are forming some sort of a disc in the sky. The research team has also been able to show that most of these satellite galaxies rotate in the same direction around the Milky Way, like the planets revolve around the Sun.

The physicists believe that this phenomenon can only be explained if the satellites were created a long time ago through collisions between younger galaxies.

“The fragments produced by such an event can form rotating dwarf galaxies,” Metz said. But there is an interesting catch to this crash theory, “theoretical calculations tell us that the satellites created cannot contain any dark matter.” This assumption, however, stands in contradiction to another observation. “The stars in the satellites we have observed are moving much faster than predicted by the Gravitational Law. If classical physics holds this can only be attributed to the presence of dark matter.” 

Or one must assume that some basic fundamental principles of physics have hitherto been incorrectly understood. “The only solution would be to reject Newton’s classical theory of gravitation,” adds Kroupa. “We probably live in a non-Newton universe. If this is true, then our observations could be explained without dark matter.” Such approaches are finding support amongst other research teams in Europe, too.

It would not be the first time that Newton’s theory of gravitation had to be modified over the past hundred years. This became necessary in three special cases: when high velocities are involved (through the Special Theory of Relativity), in the proximity of large masses (through the theory of General Relativity), and on sub-atomic scales (through quantum mechanics). 

Source: Eurekalert. The relevant papers are available here and here.


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Dark Gnat
Member
Dark Gnat
May 11, 2009 7:13 AM
Decades from now, Dark Matter will be a laughable concept, like Aether. Which is easier to prove, the existence of an invisible, immeasurable, inactive substance, or that our current understanding is simply flawed (as every previous understanding before it). It is a demonstration of an enormous ego to assume a theory is correct, and spend countless resources looking for something to back up the theory, which may be wrong in the first place. It isn’t much different than Intelligent Design in that regard. We should never assume that we are right. That said, I don’t think we need to simply jump on the dark matter-less gravitation bandwagon, as a lot of junk “science” is out there. Any new… Read more »
Jon Hanford
Member
Jon Hanford
May 11, 2009 7:30 AM
This story presented at several science news sites (and based on the Bonn University press release) seemed to be another attempt to bring MOND into the picture with no mention made of the currently accepted model of GR. This excerpt from the Phys.Org site: “The deviations detected in the satellite galaxy data support the hypothesis that in space where extremely weak accelerations predominate, a “modified Newton dynamic” must be adopted. This conclusion has far-reaching consequences for fundamental physics in general, and also for cosmological theories. Famous astrophysicist Bob Sanders from the University of Groningen declares: “The authors of this paper make a strong argument. Their result is entirely consistent with the expectations of modified Newtonian dynamics (MOND), but… Read more »
damian
Member
May 11, 2009 7:50 AM

Oh, Physorg Beat you to this one by days, Already inspired some debate there.

It would be great to consider the role of dwarf galaxies in context to the Local group and ultimately Local Supercluster of Galaxies. Is there any evidence for Lagrangian type points to Galaxies and Galaxy groups?

Let the Dark Matter games begin. smile

Jon Hanford
Member
Jon Hanford
May 11, 2009 7:52 AM
@ Dark Gnat: Above you’ve stated “It is a demonstration of an enormous ego to assume a theory is correct, and spend countless resources looking for something to back up the theory, which may be wrong in the first place. It isn’t much different than Intelligent Design in that regard. We should never assume that we are right. ” Were you referring to proponents of Plasma Cosmology, Electric Universe, Plasma Universe, and AWT, among others? Above you also stated: “I’m not a supporter of all of these alternative pseudo-science theories out there, but I do believe the current model needs to be re-evaluated.” As others have already pointed out elsewhere, the current model is constantly ‘re-evaluated’ in light… Read more »
tacitus
Member
May 11, 2009 9:04 AM

It isn’t much different than Intelligent Design in that regard.

What do you mean by this? ID is an example of a bad theory where the proponents are too ideologically hidebound to accept that there is no merit to it? If so, I would agree, but I still don’t see how that can be regarded as equivalent to Newtonian physics which at least has the merit of being true (except in very, very marginal cases).

Anaconda
Member
Anaconda
May 11, 2009 9:38 AM
Interesting… And more interesting that Universe Today was purportedly late on this story, although, I seem to remember a story similar to this in the last month or so. Jon Hanford states: ‘Were you referring to proponents of Plasma Cosmology, Electric Universe, Plasma Universe, and AWT, among others?” Hanford, that was laughable. The standard model proponents, such as yourself, espousing the gravity “only” model, or are we to say gravity “predominates” model, as electromagnetism has been confirmed by NASA to have a significant role in planetary dynamics, have attempted to “shout down” anybody that challneges their world view. “Shout down” is a debatable term, no doubt (and not all proponents have gone this way). Certainly, when it comes… Read more »
DrFlimmer
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DrFlimmer
May 11, 2009 10:07 AM
But we already knew that our galaxy is somehow “special”. The lack of globular clusters and dwarf galaxies is long known. Even our SMBH is so quiet compared to other galaxies. But what about other galaxies? We have observed many big galaxies and we found many globular clusters around them, probably 10 times or more compared to the Milky Way. When I read this theme first somewhere else, these were my first thoughts. I wonder why all the articles never mentioned the other galaxies that seem to be “normal” (whatever this means). This is a very important point: Other galaxies seem to be in agreement with “theory”. So, I think it is too quick to say: “throw everything… Read more »
Nereid
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Nereid
May 11, 2009 10:57 AM
@Dark Gnat: It is a demonstration of an enormous ego to assume a theory is correct, and spend countless resources looking for something to back up the theory, which may be wrong in the first place. I think you rather badly misunderstand what contemporary astronomy and astrophysics are about, and how they work. The whole point of research is to ask new questions, and get answers (and, if no answers were forthcoming, to rephrase the questions, over and over, as often as necessary). A lot of resources go into surveys, which may be summarised as ‘let’s take an unbiased, detailed, look’; the data from surveys, often including the raw data, nearly always are made available, for free, and… Read more »
Anaconda
Member
Anaconda
May 11, 2009 10:59 AM
@ DrFlimmer: DrFlimmer states: “Other galaxies seem to be in agreement with ‘theory’.” No. All galaxies experience rotation of the arms that is inconsistent with Newtonian gavity, if that is all that contributes to the dynamics of deep-space large structures. Maybe, it’s not so much that Man’s understanding of gravity is out of wack, but that other Fundamental Forces are acting on the large structures of deep-space? DrFlimmer states: “But we already knew that our galaxy is somehow ‘special’.” No. The Milky Way galaxy is simply at a particular stage in its electromagnetic evolution. What is interesting about this post and report is that the reported dwarf galaxies are in a placement one could postulate is due to… Read more »
Nereid
Member
Nereid
May 11, 2009 11:01 AM
@Anaconda: allow me, please, to ask you the same questions I’ve just asked Dark Gnat: Suppose you were in charge of allocating time on a major telescope, or even a dozen such, how would you go about deciding who should get time on that telescope? Suppose you have a million seconds at your disposal, on any of the major astronomical facilities, in any waveband; how would you go about deciding what to use you precious time observing? Assume, for the sake of discussion, that you have unlimited computing power, to crunch the observations from your chosen facility, in any way you wish. The only caveat I’d like to place on your (Gedunken) choices, as perfect dictator of telescope… Read more »
Feenixx
Member
May 11, 2009 11:02 AM
One of the main differences between mainstream and fringe theories seems to be: Mainstream theories are continuously being adjusted and modified by their proponents, who usually fit the description of “model agnostics”. Fringe theories are cast in stone, and their proponents have found a way to “know” that Newton, Einstein, Heisewnberg, etc were wrong. Intelligent design was mentioned as a “bad theory”. I don’t believe it’s a theory of any kind at all – it isn’t based on observation and measurement, not even on flawed observation, which would make it something I’d agree to call a “bad theory”. I reckon calling it a “conjecture” would be more appropriate. Funny that I earlier today I wrote a comment in… Read more »
Nereid
Member
Nereid
May 11, 2009 11:02 AM

@Anaconda: are you going to return to our discussion, on the other UT story? I think you promised that you would comment on what I wrote …

Sili
Member
Sili
May 11, 2009 11:03 AM
I was frustrated when I heard the SGU kibbits about this without getting some expert in for clarification. I’m now disappointed the UT hasn’t made more of an effort to elaborate (I know, I know, I’m not paying anything for the privilege of reading). But to say that it generates comments and is contrversial and then just rehash the press releases is pretty annoying. Why can’t this obsevation be modelled if there’s DM in the clusters? That strikes me as a very sweeping generalisation without much explanation for the laypeople. Sorry. DM still works pretty damn elegantly. And I have yet to hear anyone give a good explanation for the galaxy cluster collisions within a MOND framework. Why… Read more »
Dark Gnat
Member
Dark Gnat
May 11, 2009 11:08 AM
Jon Hanford I’m mearly saying that we need to keep an open mind. History has shown that new or radical scientific ideas are met with skepticism, and sometimes hostility. That said, bogus theories need to be shot down with good science, not simply dismissed outright. Dark matter has never been observed, and may not be observable at all, especially if it isn’t real. If we go for 500 years on the assumption that it does exist, and are then proven wrong, we would feel like fools. Think of the what we could have learned if we had just looked in the right places, or made sure our “measuring sticks” were accurate. Simply assuming that dark matter exist, and… Read more »
Nereid
Member
Nereid
May 11, 2009 11:09 AM
Anaconda wrote: What is interesting about this post and report is that the reported dwarf galaxies are in a placement one could postulate is due to electromagnetism being the dominant force: “the satellites should be uniformly arranged around their mother galaxy, but this is not what we found.” More precisely, all classical satellites of the Milky Way – the eleven brightest dwarf galaxies – lie more or less in the same plane, they are forming some sort of a disc in the sky. ” A torus or circular disk around the Milky Way. Just as a torus of plasma is found around the plasmoids in galaxy centers, just as toroids, “donuts”, of plasma are found to exist around… Read more »
Nereid
Member
Nereid
May 11, 2009 11:17 AM
Dark Gnat wrote: It just appears that Dark matter is becomeing a catch all for anything unexplained. Don’t know why a planet is moving a certain way? Dark Matter! Don’t know why galaxies are distributed the way they are? Dark Matter! Why does one sock always disappear in a load of laundry? Dark Matter! Again, I have no idea how you came to these conclusions, because they are little more than a grotesque parody IMHO. CDM (cold dark matter) has become a successful component of contemporary cosmological models because it provides a simple, consistent explanation, across an astonishing range of types of observations. Similarly, it is successful in studies of galaxy dynamics. Ditto wrt observations of rich clusters… Read more »
Nereid
Member
Nereid
May 11, 2009 11:19 AM

Typo:
“CDM comprises ~85% of the mass-energy of mass”
->
“CDM comprises ~85% of the mass-energy of matter”

Anaconda
Member
Anaconda
May 11, 2009 11:25 AM
@ Nereid: Dark Gnat states: “It is a demonstration of an enormous ego to assume a theory is correct, and spend countless resources looking for something to back up the theory, which may be wrong in the first place.” And Nereid responds: “I think you rather badly misunderstand what contemporary astronomy and astrophysics are about, and how they work.” Typical from Nereid: “You don’t understand “US”. No, Nereid, the truth is that you can’t see youself in the mirror as others see you. You constantly request peer-reviewed papers, but fail to acknowledge that peer-reviewed journals are a closed shop (Plasma Cosmology papers need not apply). After a while one does not waste time doing work that will be… Read more »
Anaconda
Member
Anaconda
May 11, 2009 11:47 AM
@ Nereid: Nereid, it is apparent you are an apologist for “modern” astonomy’s status quo. Have you EVER spoken out against the status quo? Just asking. Nereid, you come across as an ideological “keeper of the flame” which justifies the status quo no matter how much evidence suggests it is fundamentally worng. You quote a passage from my comment and respond: ” interesiting words.” But fail to challenge a single concept raised. Popular websites allow for altenative concepts to be raised. And you know what Nereid, there may be papers out there, there may not, but I can recognize patterns and put 2 and 2 together. Perhaps, because it matches what has been observed, and you, being informed,… Read more »
Nereid
Member
Nereid
May 11, 2009 1:04 PM
@Anaconda: Fraser requested that comments “be nice”, and I intend to do my best to keep to his request. The papers that are published in relevant, peer-reviewed journals are open, and in a great many cases, free (although you may have to be satisfied with rather older ones – access to recent papers is restricted to those who subscribe – or preprints). If an alternative idea has legs, it will get up; if someone without a connection with a research institute or university comes up with a good idea, by all means let them write it up and get it published! It’s not hard to do. Once any such good idea is published, anyone can build on it,… Read more »
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