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The Case of the Missing Dark Matter

Artist's impression of dark matter surrounding the Milky Way. (ESO/L. Calçada)

A survey of the galactic region around our solar system by the European Southern Observatory (ESO) has turned up a surprising lack of dark matter, making its alleged existence even more of a mystery.

The 2.2m MPG-ESO telescope, used in the survey. (ESO/H.H.Heyer)

Dark matter is an invisible substance that is suspected to exist in large quantity around galaxies, lending mass but emitting no radiation. The only evidence for it comes from its gravitational effect on the material around it… up to now, dark matter itself has not been directly detected. Regardless, it has been estimated to make up 80% of all the mass in the Universe.

A team of astronomers at ESO’s La Silla Observatory in Chile has mapped the region around over 400 stars near the Sun, some of which were over 13,000 light-years distant. What they found was a quantity of material that coincided with what was observable: stars, gas, and dust… but no dark matter.

“The amount of mass that we derive matches very well with what we see — stars, dust and gas — in the region around the Sun,” said team leader Christian Moni Bidin of the Universidad de Concepción in Chile. “But this leaves no room for the extra material — dark matter — that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!”

Based on the team’s results, the dark matter halos thought to envelop galaxies would have to have “unusual” shapes — making their actual existence highly improbable.

Still, something is causing matter and radiation in the Universe to behave in a way that belies its visible mass. If it’s not dark matter, then what is it?

“Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for,” Bidin said. “So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found.

“Our results contradict the currently accepted models. The mystery of dark matter has just became even more mysterious.”

Read the release on the ESO site here.

About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Comments on this entry are closed.

  • Mmmm8888 April 18, 2012, 3:56 PM

    Perhaps the black holes at the galactic centers are immensely more massive than presumed, and it isn’t the outer stars that are moving too fast, it is the inner stars that are moving too slow like how sand slows down in an hour glass to pass through a constriction. The central black hole is a spherical hole at the bottom of a spherical sand and hour glass arrangement. But, rather than sticky congestion forces due to friction, the sticky forces close in to the center of the galaxy are due to gravitational attraction between stars crowding in so close trying to get into the hole.

    • ikma April 18, 2012, 4:19 PM

      I don’t know enough about physics to say whether or not that is plausible, but another problem is that after dark matter was suggested to fix the problem you’re describing, it was found to fit exceedingly well into other theories, such as galactic formation.

    • DrFlimmer April 18, 2012, 4:50 PM

      This is not plausible. If the stars in the GC are slower than the speed to stay in orbit around the black hole, they should circle inwards. This is not observed (we have observed the entire orbit of the star “S2″ around the GC).
      Since we know the law of gravity quite well (from the solar system, for instance) we can easily infer the mass of the BH.

      • David Krauss April 19, 2012, 12:02 PM

        Observation of a full orbit means nothing.

        To adjust the hypothetical analogy, compare it to an hourglass with mixed dust, sand, and rocks. The differently sized objects will drain at different rates. Although the stars might not be dense enough to stick together well, a dense asteroid belt and gas cloud might help. And radiation pressure absorbed by the dust would support the thickened mix against gravity, allowing them to rotate slower than Kepler’s law dictates.

        The problem with the theory is that it concentrates only on the galactic center, whereas dark matter explains a phenomenon of the spiral arms.

        I wonder if this “bathtub drain whirlpool” effect has been accounted for in estimates of the galactic center’s size and distance?

        • DrFlimmer April 20, 2012, 8:22 AM

          It is still not plausible.

          In order for the SMBH at the GC to have an effect VERY FAR away (i.e. where we are) it must be MUCH bigger and MUCH more massive. The orbital speed of the star “S2″ would therefore be nowhere near a stable orbit. It should be gone entirely now.
          Not the least since it orbits the GC at a distance comparable to that of Pluto to the Sun. If the SMBH would be massive enough to influence large parts of the galaxy, its event horizon would be tremendously bigger than it actually is. “S2″ should not even exist under such conditions (and tidal forces are not yet taken into account).

    • James_Dwyer April 20, 2012, 3:15 PM

      As I understand, the fundamental problem is that the galaxy rotation problem presumes that disk objects orbit the central mass of the galactic bulge and must comply with Kepler’s laws of planetary motion, exhibiting rotational velocities that diminish as a function of radial distance.

      Newton showed that Kepler’s equations depend on orbital bodies whose mass is a negligible fraction of total system mass to avoid interactions with other orbitals (planets). The Sun contains 99.86% of total Solar system mass.

      Neither the SMBH nor all the other objects within the galactic bulge (some large spiral galaxies do not have a central bulge) represent anywhere near such a dominating majority of total system mass: very large percentages of total galactic mass is contained within the galactic discs.

      Disc objects must primarily interact gravitationally with all the other disc masses: the disc is self-gravitating; disc objects do not independently orbit any center of mass, they collectively rotate.

      In other words, spiral galaxies are not planetary systems and the ‘laws’ of planetary motion are not universal laws. It has never been formally established that the laws of planetary motion or Keplerian rotational curves should apply to spiral galaxies.

      • ft_c April 21, 2012, 9:22 AM

        Excellent!

      • DrFlimmer April 21, 2012, 12:23 PM

        I don’t think that astronomers have been “that stupid”. The near Keplerian motion stems from the fact that the the further out from the center you are the less dense the disk will be. Interestingly, and it should apply here as well for at least a first order approximation, the gravity an object feels depends on its orbit and the accumulated mass inside that orbit. It doesn’t really matter where that mass is located, as long it is inside the orbit. The mass outside the orbit does not correspond to that equation, as long as it is more or less evenly distributed, which is a fair assumption for a galaxy.

        This results in what I called a “near Keplerian” motion. And it should result in a drop in the rotation curve and not in a flat one.

        • James_Dwyer April 21, 2012, 6:43 PM

          It’s certainly not an issue of anyone’s stupidity or competency as astronomers, and I never said that it was. I’m not a physicist, but I have examined the early research reports. Vera Rubin and her collaborators simply presumed that the velocity of spiral galaxy disc objects should be consistent with Keplerian rotation curves – as she often said, “just like planets in the Solar system.” As stated in http://en.wikipedia.org/wiki/Laws_of_planetary_motion#History
          “Some eight decades later, Isaac Newton proved that relationships like Kepler’s would apply exactly under certain ideal conditions that are to a good approximation fulfilled in the solar system, as consequences of Newton’s own laws of motion and law of universal gravitation. Because of the nonzero planetary masses and resulting perturbations, Kepler’s laws apply only approximately and not exactly to the motions in the solar system.”

          Objects within a galactic disc do not independently orbit a center of mass – they primarily interact gravitationally with neighboring masses. As I understand, dark matter halo models assume that the majority of ‘missing mass’ is outside the galactic disc in order to affect a flat rotation curve, preferentially affecting peripheral disk objects.

          Alternatively, please see:
          Feng & Gallo, (2011), “Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies”,
          http://www.raa-journal.org/raa/index.php/raa/article/view/858

          Jalocha et al, (2011), “Vertical gradients of azimuthal velocity in a global thin disk model of spiral galaxies NGC 2403, NGC 4559, NGC 4302 and NGC 5775.”, doi:10.1111/j.1365-2966.2010.17906.x, http://arxiv.org/abs/1006.2060v2

  • John Henle April 18, 2012, 4:17 PM

    “Our results contradict the currently accepted models”
    If our observations of the physical world don’t match the currently accepted models, and we can’t find any invisible/imaginary “stuff” to explain the difference, maybe the currently accepted models aren’t right.

    • Eric Scott Sembrat April 18, 2012, 5:09 PM

      Isn’t that precisely what this article is implying?

      • Torbjörn Larsson April 18, 2012, 9:13 PM

        Who knows what it is implying, the research team seems overreaching in their claims as I note in another comment. You can deduce anything from a faulty premise.

    • Jim Buttazzoni April 18, 2012, 10:47 PM

      that is why they call them scientific theories, not scientific facts.

    • TheDirtBoy April 19, 2012, 1:48 AM

      It seems like common sense to people like you or I but try telling that to the scientists. It’s not even like this is a new concept, main stream science being dead wrong, the only difference now is your not put to death as a heritic when you come up with a competing theory. You still have the same ego and the same refusal to admit your mistakes. You would think by now we would have learned that we are not the pinnacle of creation, we are not infallible and the universe does not infact revolve around us. Obviously I’m mistaken.

  • SgtBeavis April 18, 2012, 5:28 PM

    This is why I love science. Just when you think you’ve got something figured out, you get a new curve ball…

    • andrew g April 19, 2012, 3:51 PM

      Or a googly for UK readers. Maybe even a doosra :o)

  • Abraham Samma April 18, 2012, 6:00 PM

    Most assuredly the alleged dark matter has become more of a mystery than a fact. This observation I dare say might be suffering from a case of distribution bias; maybe dark matter isn’t as widespread IN the galaxy as thought. It may be concentrated in some places and non-existent in others. I admit ignorance on how dark matter is actually thought to behave other than what has been mentioned in the article.

    Maybe now might be a good time to reconsider modified newtonian gravitation?

    • Torbjörn Larsson April 18, 2012, 9:05 PM

      How can you assure something a) that isn’t a fact, see my comment above, b) without having any reference backing up such a remarkable claim?

      Just a few months ago the first successful simulation of spiral galaxies including their peculiar structure (the Eris simulation, google it because it is truly a beautiful youtube) showed that precisely dark matter was the missing factor for such simulation.

      That kicked out the abominable MOND, that has lurked well beyond its “best before” date as simplistic models of galaxy rotation. Now standard cosmology and dark matter predict _all_ structure formation down to star clusters I believe – then planetary system formation models take over.

      On MOND and its support structure, as I recently saw John Cleese say in a talk of creativity on behavior of authority figures of all kinds: “Pppbbbrrrrrtthhhhhh”! Sorry, I like Cleese.

      • ft_c April 20, 2012, 2:18 AM

        One simulation is certainly not proof of anything, Eris was tweaked an awful lot and goes to show only that we can, in our limited knowledge, cobble together a system that can force a replication of what we see in nature. It was the reverse engineering production process that got it to where it is, the pretty familiar spiral. Eris isn’t worth much for DM (or anything other than to look at and marvel), especially if you consider that each particle in the simulation (that is, a chunk of dark matter say, or cloud of gas) weighs about 4000 suns! It has also been shown that DM must remain in a stationary halo if it were to keep a galaxy stable. So does dark matter also break the speed limit by escaping the event horizons of black holes?! Either that or it is not affected by gravity in order to remain in it’s pretty halo. In which case, it’s useless… This has got to be some pretty amazing stuff! We’re also looking for a substance which does not interact with the electric or magnetic fields, but when it annihilates it turns into electromagnetic radiation. It really can do whatever it wants. It’s a very messy, bitty theory. I’d certainly say it’s a dead end

    • Peter A. LaChance April 20, 2012, 5:02 PM

      It takes scientist a long time to give up one their conjured beliefs. If you are looking
      for a cat and a mouse appears you convince yourself their must be a cat somewhere,
      or perhaps miss the cat altogether because it wasn’t what you were looking for.
      People who begin looking somewhere else to answer their bewilderment are
      belittled for not following in lock step.

  • thylawyer April 18, 2012, 6:01 PM

    I suspect it has more to do with how gravity is changed as the local “cloud” of matter increases.

  • Zoutsteen from Holland April 18, 2012, 6:59 PM

    instead of gravity, might we look at time?
    example: 1 atomic clock on closest side of the moon, 1 atomic clock of far side of the moon …..

    The galaxy as a whole is a bit bigger than the moon, of coarse.

  • Torbjörn Larsson April 18, 2012, 8:54 PM

    At least at first glance it seems that Bidin is overstating their find:

    1) It is not a recent find. This is based on a simplistic model of our galaxy as it applies to our neighborhood by way of a Poisson mass source equation on the thin disk, thick disk and halo, and I can find sources going back to 1998, pre-standard cosmology, that there is no need for a dark matter term in it.

    At best they have quantified the previous null result more.

    2) This is not a direct observation of dark matter as other mass methods like gravitational lensing, which images dark matter in the same way that an atomic force microscope images the atoms on a surface.

    It is very indirect, as mentioned the method used is simplistic to say the least, and I don’t know how sensitive it is to model parameters other than dark matter. If one puts in dark matter, what parameter would then be strained?

    Maybe the thick disk, which at least as of 1998 had no direct observation method. I’ll find it likely that we can image dark matter much better than the thick disk.

    So yes, it is interesting, but maybe not a problem as much for dark matter as for the Poisson mass model of the Milky Way.

    • James_Dwyer April 20, 2012, 2:36 PM

      Aside from the ever debatable results of necessarily complex gravitation simulation models, there are observational conflicts with the existence of enormous shells of galactic dark matter. In particular, observations that visible Milky Way halo objects do exhibit Keplerian rotational curves severely constrains the location of most galactic mass, including any potential dark matter halo, to the diameter of the disc.

  • ???????? ???????????? April 18, 2012, 11:56 PM

    Isn’t the Universe a beauty to behold? Every time we hang up a theory on the wall, rest-assured it explains something, the Universe comes by and unhooks it!

    • Ancient Brit April 19, 2012, 6:38 AM

      Actually, the Universe doesn’t – we do. Scientists are their own worst enemy – and that’s how it should be.

    • andrew g April 19, 2012, 3:54 PM

      Don’t get carried away. Mightn’t this be more like the superluminary neutrinos result? In fact almost certainly so.

  • Dennis Patterson April 19, 2012, 2:03 AM

    I feel that “dark matter” is so misunderstood by us and beyond our understanding as the upper sky, space and the heavens were to the Greeks who called this region “Aether.” One day we will have the answer, and mankind will look back on our ideas of “dark matter” as quaintm and simple.

  • Prism2Spectrum April 19, 2012, 11:53 AM

    “Dark Matter” (DM), the “substance” that presumably “upholds” galactic shapes, yet is undetectable beyond the GRAVITY effects. Could it be that what is actually missing, is some facet of understanding that would account for the gravity – without resorting to Mass? Illogical, perhaps.

    Could it be a Force sustaining galaxy forms, not tied to Matter, but possible related to Energy (if that is not contradictory)? And further, could it be kin to “Dark Energy” – if that property too, does not reflect some aspect of missing knowledge – a gap in understanding?

    Indeed, could it be unrelated to both Energy-Matter? 80% is a lot to be “missing”. Something is not computing, somewhere.

    “…but dark matter now also forms an essential component of theories of how galaxies formed and evolved.” – Formation Models that may eventually have to be overhauled. “But a new study [ MW star motion, and search of Sun's proximity(?) ] by a team of astronomers in Chile has found that these theories just do not fit the observational facts.” …. “ ‘Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for. So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found. Our results contradict the currently accepted models.’ ” – Christian Moni Bidin (Science Daily)

    DM has struck me as inelegant; I for one will not be unhappy if it turns out the Astronomers where looking in the wrong direction (as long suspected).

    “Still, something is causing matter and radiation in the Universe to behave in a way that belies its visible mass. If it’s not dark matter, then what is it?” – J. Major. Could this mystery be explainable by an “Unknown Force” (as one old SD article title asks)?

    ( No assertions, just rhetorical questions. )

  • squidgeny April 19, 2012, 12:16 PM

    I have a question for people who know about these things.

    It’s my understanding that out of the ‘quantum vacuum’, matter appears in matter-antimatter pairs (before near-enough instantly annihilating and returning the energy it ‘borrowed’ from the universe)

    For the brief moment such matter exists, would it exert a gravitational pull? If so, do we have any idea of how much a pull it would have and whether this has any contribution to what we think dark matter is responsible for?

  • Dennis Patterson April 19, 2012, 6:21 PM

    We don’t understand it because we aren’t suppoed to understand it yet. There are probably “issues” surrounding this “dark matter” (or whatever it is) that would prove inherently dangerous to our existence. Knowledge of this “substance” may revolutionize our concept of the universe or even our technology and at the same time prove a threat to our very existence as a civilization.. Look at what man has done with the knowledge of the atom. . . . . .

  • Dennis Patterson April 19, 2012, 6:36 PM

    “1.21 Gigawatts!!!!!! 1.21 Gigawatts!!!!!! Great Scott!!!!!! How could I have been so careless!!!!!” — Dr. Emmett Brown

  • Dennis Patterson April 19, 2012, 6:43 PM

    Perhaps we don’t understand it yet, because we are not “supposed” to understand it yet. Discovery of this so called “dark matter” (if that is indeed what it is) could pose a grave danger to our existence. Knowledge of dark matter might very well revolutionize our understanding of the Universe, and perhaps revolutionize our technology; but it might also constitute a threat to our continuance as a civilization. Look at what mankind has done with the knowledge of the atom. . . . . .

    • squidgeny April 19, 2012, 8:20 PM

      Look at what mankind has done with the knowledge of anti-matter: medical breakthroughs that have saved countless lives (and not a single “anti-matter weapon” in sight, because it’s impractical)

      Knowledge of dark matter might just as easily save us all and give us eternal bliss. Until we actually go out and know about it, who’s to say what the result will be?

      • Dennis Patterson April 19, 2012, 11:12 PM

        Indeed. . . . . .

      • bugzzz April 20, 2012, 1:01 AM

        Agreed. All scientific / technological progress is a double sided anyway. Risks and rewards hand in hand.

  • bugzzz April 19, 2012, 7:55 PM

    Here’s an idea with no scientific basis whatsoever. What if the missing matter is an ‘intelligence’ that holds the universe together? And/or what if this intelligence is not a constant? Just b/c other things are constants why should we presume something we know so little about is also a constant? We clearly do not understand dark matter in even a primitive way, which is pretty wild considering how much we already DO know about the universe.

    • Ancient Brit April 20, 2012, 12:45 AM

      So the flipside is: what if there’s an intelligence that is flinging the universe apart? That would have to be the corollary, in order to define dark matter’s alter ego: dark energy.

      And it too would not necessarily be a constant (except as constant acceleration) although common sense dictates that both would probably have to be, since it appears from my reading that dark matter/dark energy have the same relationship as ordinary matter/energy (i.e., one can convert to the other).

      • bugzzz April 20, 2012, 1:05 AM

        Right. Is it not possible that, given 5 billions years of existence, prior to us that a biological civilization developed artiicial intelligence and its inorganic creations (imperceptible because of their nanotech developments) adopt as their mission the preservation and

        • Ancient Brit April 20, 2012, 2:40 AM

          Except that dark energy seems to be “winning” – it is pushing the fabric of the universe apart at the highest level even as dark matter holds “smaller” structures such as galaxies together. The net result will be that at some point our view of the “universe” will revert to what it used to be – namely that the universe consists solely of our galaxy.

          • bugzzz April 20, 2012, 8:36 AM

            Not necessarily if this imagined intelligence slows the rate of expansion at some point. If there’s some “active engineering” going on then the expansion can be slowed as well.

          • Ancient Brit April 20, 2012, 12:47 PM

            If there was evidence that the expansion was slowing then your hypothesis would have some support, but as I understand it the acceleration is itself accelerating so someone has their foot pressed hard on the gas pedal…

  • SandraL April 20, 2012, 8:25 PM

    Maybe it’s time to revisit the old “cosmic ether” theory. After all, Michelson and Morley could have gotten it wrong. ;)

    It’s always more interesting when hypotheses fail – that means there’s something new to learn.

  • Ettore Greco April 21, 2012, 7:22 AM

    Since the time of Galileo, anytime a scientific theory has challenged one religious dogma, science has always had to yield before Religion. Often, the same scientists are compelled to yield to Religion.
    An example was when Einstein became alienated by the concept of Quantum mechanics because he didn’t want to accept a “World of probabilities” contrary to his Jewish Religion. This happened even after this new discovery had revealed the key to comprehend the Universe.

    It would seem that Religious scientists are those less likely to find that objectivity needed to recognize the origin of the Universe.
    In fact, modern scientists have introduced new theories but, like also in the past for Einstein, the promoters of Standard Model (Sheldon Lee Glashow and Steven Weinberg) and String Theory (Leonard Susskind) are Jewish scientists strongly supported by the media which popularize these theories even if they are both inconclusive when attempting to explain the Creation of the Universe from those conditions. In their theories, these scientists are trying to explain the Creation with particles of atomic mass already existing at the time of the Big Bang, like also Einstein sustained (adding only to more confusion).

    In effect, energy in form of atoms did not exist under the heat and pressure at the time of the Big Bang.
    Back then there was only energy in form of waves and in no other way the Creation can be explained.
    Waves, after having long traveled and dispersed part of their original energy, had transformed into atoms (Wavevolution) which eventually formed the whole Universe, including the human being.

    The wave, origin of the atom, is also the original building block of Humankind.

    http://www.wavevolution.org

  • Robert Becker April 21, 2012, 4:49 PM

    very interesting and complicated subject. I enjoyed reading all the below views,questions, and explainations. My 2 cents worth is just that the universe is very complex and massive beyond anyone’e belief. I admire people/scientist who try to figure things out and make sence of all of it. Theories are amazing things, however just because they can not be disproven, neither can they be proven. They all seem at times to work, but time means nothing to the universe and man has been here for an extremely short time. It is possible that we think we are doing everything right because things seems to suggest it is right, but maybe we are looking at everything wrong. Just my thought.

  • Edward Roberts April 26, 2012, 3:15 PM

    This is an interesting data point in a very complex area of study. Quoting from the paper’s conclusion: “We feel that any attempt to further interpret and explain our results, beyond that presented in this paper, would be highly speculative at this stage.”

    Reminds me of the kerfuffle around the OPERA faster-than-light neutrino study. They, too, warned against premature conclusions, which warning was widely ignored.

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