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Astronomers Find 19 More Galaxies Missing Their Dark Matter (astronomy.com) 90

Posted by BeauHD from the missing-piece-of-the-puzzle dept.
A reader shares a report from Astronomy.com: Astronomers have discovered 19 more galaxies missing their dark matter. Instead of dark matter, these strange galaxies are mainly filled with regular matter, like the protons, neutrons, and electrons that make up everything we're familiar with. The new find, published November 26 in Nature Astronomy, bolsters the controversial recent discovery of two other galaxies without dark matter. The mysterious substance accounts for most matter in the universe, and it's thought to be the primary component of all galaxies -- as well as the main driver of galaxy formation in the first place. So, finding so many galaxies without the exotic matter suggests astronomers are missing something major about how galaxies form and evolve.

"This result is very hard to explain using the standard galaxy formation model," said lead author Qi Guo of the Chinese Academy of Science in a press release, "and thus encourages people to revisit the nature of dark matter." The latest batch of galaxies missing dark matter was discovered when Guo and her team explored the nature of 324 dwarf galaxies using data from the Arecibo Observatory in Puerto Rico and the Sloan Digital Sky Survey. With this data, they followed in the footsteps of Rubin and Ford, studying how fast hydrogen gas rotates around each galaxy. They also calculated how much normal matter -- in the form of both gas and stars -- they contained. After crunching the numbers, Guo and her colleagues determined that, of the 324 dwarf galaxies they investigated, 19 of them contain enough visible matter to solely explain the motions of the galaxies' hydrogen. In other words, a lot of dark matter seems to be missing from these galaxies.
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Astronomers Find 19 More Galaxies Missing Their Dark Matter

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  • Dark matter....dark energy (Score:5, Insightful)

    by Papaspud ( 2562773 ) on Saturday December 14, 2019 @02:43AM (#59518238)
    It seems like the more we look at the visible universe, the more we need to realize we are probably very wrong about a lot of stuff. Between this, the variable expansion rate of the universe and the star that seems to be older than the universe..... those are just the ones that come off the top of my head- there are a lot of new theories that need to be worked out.

    • Re:Dark matter....dark energy (Score:4, Insightful)

      by Aighearach ( 97333 ) on Saturday December 14, 2019 @03:44AM (#59518276)

      Maybe in the end it was unwise to invent new physics to explain the incorrect astronomical predictions.

      Especially now, when the new physics still leads to incorrect astronomical predictions.

      • Re: Dark matter....dark energy (Score:5, Insightful)

        by Aristos Mazer ( 181252 ) on Saturday December 14, 2019 @08:32AM (#59518486)
        No one has invented anything. The hypothesis of dark matter is simply the current best fit for the data available. There definitely seems to be mass out there that we cannot account for. It moves in predictable orbits. It in so many ways to behave like matter. If a stronger hypothesis comes along, physicists will move to that. For now, the best description of the phenomenon observed - not invented - is dark matter.

        • If you "know" it is there merely because you fit the idea to the data, I dispute that you even have a hypothesis.

          • We do have direct observations of dark matter through telescopes. We do know it exists.
            The image [briankoberlein.com] shows a false-color representation of dark matter in six different galaxy clusters. Just as we can’t see infrared directly, but can detect it’s presence through CCD camera, we can detect dark matter by its gravitational effects on background light. The images are part of a recent work that analyzed the dark matter distribution in 72 colliding galaxy clusters. The results have further defined the n

            • Not trying to flame you but there really isn't any gentle way to put this. Learn about something before you stupidly post on it.

              Your first image is, the Crab Nebula in various wavelengths of light. Lets just pass that one as a mistake.

              The second isn't false color imaging of dark matter. It's an image created by saying a matter distribution must be created by dark matter, fitting the data back to the hypothesis and saying dark matter should be here but we can't see it because it only interacts gravitationall

      • Re:Dark matter....dark energy (Score:5, Insightful)

        by burtosis ( 1124179 ) on Saturday December 14, 2019 @09:19AM (#59518530)
        I think you have this backwards. Traditional physics started failing, first noticed in galaxy rotation rates, and then in how galaxies move. Kind of insane to think the 0.01% of galaxies stripped of dark matter are the only “correct” ones because they behave accordingly. The solution isn’t to not look for a solution while covering your eyes and ears, it’s to carry on the scientific method by proposing new theories that fit all the data to date. Follow those models novel predictions and see if they fit observation, if so you have an expanded and more accurate theory.

        • There is no experiment involved, merely observation of events from the distant past that can't be replicated, so physics didn't fail at all.

          Astrophysicists failed to understand things distant, and they continue to fail to understand things at that scale. They just went from not even knowing, to being wrong about all the details.

          Every new astronomical instrument that can see something new still uncovers stuff they didn't know. The only problem is, they already claimed to have answered everything!

          If you compa

          • Re: (Score:3)

            by Ost99 ( 101831 )

            1) No one ever claimed to have answered everything. That's not how science works.

            2) Science does not require experiments. Science requires TESTABLE hypotheses.

            Experiments are not required for a hypothesis to be testable. Making predictions that can be tested by new observations is the modus operandi for the scientific process. In astrophysics we get new observations to test the hypotheses all the time. Sometimes a hypothesis is wrong and must be adjusted or replaced, that's not something to be ashamed of. T

        • Re: (Score:2)

          by jabuzz ( 182671 )

          Get back to me when the astrophysicists stop modelling galactic rotation using Newtonian mechanics. Until that time modeling galactic rotation using a known incomplete model of gravity and then claiming that it does not work and there must be the ether of matter fails Occam's razor. That and the fact there is something special about the local area in this galaxy so there is no dark matter despite it making up 2/3rds of the matter in the Universe.

          It is my understanding that this is one of the things they wan

      • Maybe in the end it was unwise to invent new physics to explain the incorrect astronomical predictions.

        There are basically three possibilities. They are: 1) our observations are wrong, including the observations of 305 out of the 324 galaxies in this study . This is technically possible but wildly improbable given we have an absolutely enormous number of observations using dozens of telescopes analyzed by dozens of groups all arriving at the same conclusions. 2) Our known physics is complete and correct, but is being applied incorrectly to yield incorrect results. Given hundreds, maybe thousands, of very int

      • Re: (Score:2)

        by habig ( 12787 )

        Maybe in the end it was unwise to invent new physics to explain the incorrect astronomical predictions.

        Especially now, when the new physics still leads to incorrect astronomical predictions.

        Of course, there were the 305 other dwarf galaxies in this survey for which the dark matter hypothesis works just fine - read TFA. Something interesting is going on, probably with our (currently sketchy) models fo galaxy formation. But, dark matter being right out is not the leading candidate: otherwise, what's going on with the vast majority of galaxies? So far this has only shown up in looking at dwarf galaxies: so, the question could relate to "what makes dwarf galaxies dwarfy?"

    • I haven't heard about it yet.

      • Methuselahs star- https://www.space.com/20112-ol... [space.com]
        • I was piqued by the question too.

          Ignoring Space.com because it has some really shit anti-adblocking UI, I got the catalogue number "HD 140283" before the shit UI kicked in. I think the relevant paper is

          Journal reference: Astrophys. J. 765, L12, 2013
          DOI: 10.1088/2041-8205/765/1/L12
          Cite as: arXiv:1302.3180 [astro-ph.SR]

          available at https://arxiv.org/abs/1302.318... [arxiv.org]

          The author's summary (not space.com, or whoever wrote the "popular" summary) states several relevant points immediately :

          The quoted error includ

    • Proves, rather than disproves dark matter. (Score:5, Insightful)

      by Richard Kirk ( 535523 ) on Saturday December 14, 2019 @05:45AM (#59518366)

      This is not in fact as surprising or controversial as the press love to make out.

      The original evidence that convinced many of us that what we called 'dark matter' was the 'Bullet nebula' in the Abell cluster, where the dark matter, as imaged by the red-shift of the galaxies behind it, did not follow the visible mass of two galaxies that had narrowly missed each other. Before that, all the errors we had seen were from galaxy rotations, and these could be explained as some fine tweak in the gravitational constant at galactic distances. But this showed the dark stuff could be 'flung' off when the visible matter is stopped by other visible matter. It is not surprising that galaxy formation may have the same irregularities in dark matter distribution. If you have a cloud of material that condenses onto two galaxies that fly apart, the dark matter may well not get split evenly. Probably buried in this data is some clue as to dark mater interaction, but we are not there yet.

      On the other hand, if you don't want to believe in 'dark matter' as actual stuff, then how would you explain the two sorts of rotation they find in galaxies?

      Dark matter must have some interactions with itself or it would not be clumped like this. We do not have any to study, but we can simulate some likely forms of self-interaction, and can model

      • On the other hand, if you don't want to believe in 'dark matter' as actual stuff, then how would you explain the two sorts of rotation they find in galaxies?

        Dark matter isn’t a binary variable. There isn’t an “on” and “off” state. None of the galaxies observed are fully stripped 100%, it is simply a continuous function. Functionally, the interactions play out as if a cloud of non-interacting (except through gravity) massive particles envelops the whole galaxy though it’s distribution remains a mystery.

        Dark matter must have some interactions with itself or it would not be clumped like this. We do not have any to study, but we can simulate some likely forms of self-interaction, and can model

        It is wrong to think dark matter must be self interacting [iop.org]. Although we don’t have enough evidence to say ei

        • Dark matter isn’t a binary variable.

          This is true. I was trying to keep the explanation short, and to match the original article. Now that people know to look for them, they have fund a number of galaxies that are 'light' in dark matter. I agree, it is unlikely that they have zero matter - just that some sort of slingshot process may have partitioned their matter differently. Presumably there are other galaxies with a double helping of dark matter.

          Dark matter must have some interactions with itself or it would not be clumped like this. We do not have any to study, but we can simulate some likely forms of self-interaction, and can model

          Ah. You got me on that one. This was a sentence that got lost off the bottom of my editor. I had

          • Well, I conflated MOND with WIMPS in some kind of brain fart today and I’d like to think we’re even. I can’t think of a way it couldn’t be at least far more weakly self interacting than baryonic matter if we are looking at the bullet cluster properly. If we can figure out the shapes it forms around galaxies that should give us a good clue.

          • Presumably there are other galaxies with a double helping of dark matter.

            Yes, we have several candidates for such a thing "dark galaxies", not even counting the ultra-faint dwarfs [arxiv.org] that appear very common (based on our observations in the Local Group) and appear very likely to all be dark matter concentrations with very little baryonic matter.

            The truth of the matter is that evidence for the reality and ubiquity of dark matter is piling up very fast. There is no credible basis for dismissing its reality. There will be some hold-outs of course among real scientists, as there always

    • Astronomers Find 19 More Galaxies Missing Their Dark Matter

      Nobody leaves the room! And Jones, if I find out it was you again, there'll be a parent-teacher meeting in short order.

    • Re: (Score:3)

      by Junta ( 36770 )

      Well at leas the Methuselah star doesn't *necessarily* show a discrepency with the age of the universe (while the age is older, it is '+/-' 800 Million of error, which means it doesn't confidently conflict with the other measurement.

      The point still stands that we have a lot of missing knowledge and best-guess stand-ins to fill gaps, but currently the star does not necessarily present an indiscrepancy in and of itself.

  • Dark Energy, Dark Matter (Score:2, Interesting)

    by Anonymous Coward
    One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence. Then one version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because th

    • Re:Dark Energy, Dark Matter (Score:5, Informative)

      by Anonymous Coward on Saturday December 14, 2019 @03:07AM (#59518250)
      What Is Dark Matter?

      By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, scientists have come up with the composition that we described above, ~68% dark energy, ~27% dark matter, ~5% normal matter. What is dark matter?

      We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.

      However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs". But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles). https://science.nasa.gov/astro... [nasa.gov]

      • The wimp model has been dead since at least 2010. The article above is simply 19 more nails in its coffin. RIP wimp theory, I’d miss you but it’s like we’ve never interacted.
        • Sorry meant mond^ not wimps. Pre coffee error.
          • MOND wasn't mentioned. It's not entirely dead, but there are only a fairly small number of people working on it. I did a search on Arxiv a while ago and came up with something in the order of a dozen papers per year. Which is slightly more vivacious than a Norwegian Blue [wikipedia.org]. Slightly.

      • Baryonic matter could still make up the dark matter if it were all tied up in brown dwarfs or in small, dense chunks of heavy elements. These possibilities are known as massive compact halo objects, or "MACHOs".

        ... and the observational searches for MACHOS carried out over the last 35-odd years (that I've been watching, anyway) really aren't coming up with enough such matter to balance the cosmological books. They are there, but not enough of them.

  • Sure, the galaxy-formation theories need changing. (Score:5, Interesting)

    by SEE ( 7681 ) on Saturday December 14, 2019 @04:26AM (#59518306) Homepage

    The galaxy-formation theories are all about a step and a half up from wild-ass guesses. The current galaxy-formation theories failing to stand up to new observations is about as surprising as a snowstorm in Michigan in January.

    The important thing is, these cases of missing dark matter make it all the more certain that the cause of the observations that led to the dark matter hypothesis is indeed a matter of a real form of matter that makes up part of the composition of most galaxies.

    If the problem with our observations was that General Relativity was wrong at large scales, that the real law of gravity was different, then every galaxy without fail would follow the different gravitational law, and thus they would all move the same way. If a small minority of galaxies move differently, though, that tells you that the issue is a difficult-to-observe factor in the composition of galaxies.

  • Simplest explanation.. (Score:5, Funny)

    by h33t l4x0r ( 4107715 ) on Saturday December 14, 2019 @04:26AM (#59518308)
    The inhabitants of those galaxies have been using dark matter to power their cars. Now they're probably frantically switching to renewables.

  • Could it be missing because it was used as a fuel source?

  • Galaxy: "Dark matter? We ain't need no stinkin' dark matter!"

  • The SciFi -- excuse me, SyFy -- channel is missing its Dark Matter [wikipedia.org] too.

  • Call it for what is experimentally observed: blahblahblah discrepancy.

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