Citizen scientists re-tune Hubble’s galaxy classification

Royal Astronomical Society

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IMAGE: Spiral structure in the Pinwheel Galaxy (Messier 101), as observed by the Hubble Space Telescope. view more

Credit: NASA, ESA, CXC, SSC, and STScI

Hundreds of thousands of volunteers have helped to overturn almost a century of galaxy classification, in a new study using data from the longstanding Galaxy Zoo project. The new investigation, published in the journal Monthly Notices of the Royal Astronomical Society, uses classifications of over 6000 galaxies to reveal that “well known” correlations between different features are not found in this large and complete sample.

Almost 100 years ago, in 1927, astronomer Edwin Hubble wrote about the spiral galaxies he was observing at the time, and developed a model to classify galaxies by type and shape. Known as the “Hubble Tuning Fork” due to its shape, this model takes account of two main features: the size of the central region (known as the ‘bulge’), and how tightly wound any spiral arms are.

Hubble’s model soon became the authoritative method of classifying spiral galaxies, and is still used widely in astronomy textbooks to this day. His key observation was that galaxies with larger bulges tended to have more tightly wound spiral arms, lending vital support to the ‘density wave’ model of spiral arm formation.

Now though, in contradiction to Hubble’s model, the new work finds no significant correlation between the sizes of the galaxy bulges and how tightly wound the spirals are. This suggests that most spirals are not static density waves after all.

Galaxy Zoo Project Scientist and first author of the new work, Professor Karen Masters from Haverford College in the USA explains: “This non-detection was a big surprise, because this correlation is discussed in basically all astronomy textbooks – it forms the basis of the spiral sequence described by Hubble.”

Hubble was limited by the technology of the time, and could only observe the brightest nearby galaxies. The new work is based on a sample 15 times larger from the Galaxy Zoo project, where members of the public assess images of galaxies taken by telescopes around the world, identifying key features to help scientists to follow up and analyse in more detail.

“We always thought that the bulge size and winding of the spiral arms were connected”, says Masters. “The new results suggest otherwise, and that has a big impact on our understanding of how galaxies develop their structure.”

There are several proposed mechanisms for how spiral arms form in galaxies. One of the most popular is the density wave model – the idea that the arms are not fixed structures, but caused by ripples in the density of material in the disc of the galaxy. Stars move in and out of these ripples as they pass around the galaxy.

New models however suggest that some arms at least could be real structures, not just ripples. These may consist of collections of stars that are bound by each other’s gravity, and physically rotate together. This dynamic explanation for spiral arm formation is supported by state-of-the art computer models of spiral galaxies.

“It’s clear that there is still lots of work to do to understand these objects, and it’s great to have new eyes involved in the process”, adds Brooke Simmons, Deputy Project Scientist for the Galaxy Zoo project.

“These results demonstrate that, over 170 years after spiral structure was first observed in external galaxies, we still don’t fully understand what causes these beautiful features.”

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From EurekAlert!

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59 thoughts on “Citizen scientists re-tune Hubble’s galaxy classification

      • Mighty dry humor coming from Florida. There ought to be a dance called The Electric Universe, I’d get a charge from that.😉
        (Going to rename my band “The Thunderbolt Project”.)

        • Yes, Pop, I was wondering about EU since their computer models also produce spiral structures.

          Ah, I love the ubiquitous:

          we still don’t fully understand

          That’s technical scientific jargon for we have no idea and are still splashing around in the paddling pool of hypotheses. ( More money needed to “fully” understand this ).

    • jarryd,
      Unlikely – electrostatic forces diminish exponentially by distance and so couldn’t have much of an effect at astronomical distances. Perhaps within a solar system, but generally stars are just too far apart.

      • Not quite, as Electrostatic forces are subject to Inverse-Square, just like Gravity. However, unlike gravity, they come in two flavors, plus and minus, and always in equal amounts over anything more than a “small” distance. On the scales of galaxies, they certainly cancel out.

        Gravity sucks. Seemingly, for our purposes, at least, that is *all* it does. So even though it is the weakest force, it has the most, uh… “Universal” impact.

        • They’re formed by the ejection of quasars from the galactic core perpendicular to galactic plane and then pulled back back down galactic plane by the magnetic field of the galaxy. They then spin off to form the spiral arms.

        • There’s 400,000 Volt potential difference between the surface of the Earth and the top of the atmosphere. The electric field is in the direction of the Earth, which means positive charges are being pushed in the direction of the Earth which is negatively charged. In order to maintain the potential difference, lightning delivers negative charge to the surface. The lightning world wide is a maximum at 7pm London time, and a minimum at 7am London time. In short, there’s roughly 200 Volt potential difference between your feet and your nose. Since you’re grounded, you don”t notice it.

          • I’ve been on the edge of a desert plateau with my wife’s and her friend’s hair both sticking straight out from the static of the nearby thunderstorms, sure. Time to get out of Dodge! But you get to the moon, and there is no noticeable effect of all that static charge separation. Draw a big enough circle around all those separated charges and you come up with net zero excess charge. They balance, so they have no consequence beyond their “immediate” vicinity. For every electron, there is a proton, usually somewhere within a star’s radius or so. It’s hard to get enough charge separation to move planets, or even reasonably-sized asteroids: it always reaches the point where it finds a break-down path and it goes to ground, as you say.

          • cinaed
            June 12, 2019 at 5:34 pm

            The electric field is in the direction of the Earth,
            ——————
            cinaed,
            Allow me to express my understanding in consideration of points put forward in your comment.

            First, I think it may help when considering “the electrical field” as you put it,
            in the requirement of it to be considered as per the context of “electrostatic”…
            as very well the “field” thingy there, may clearly suggest.

            Second, when considering the following part of your statement as below:

            “which means positive charges are being pushed in the direction of the Earth which is negatively charged.”
            ——–
            I think, it may still help to consider that ” positive charges ” versus “negative charges.”
            is simply an “arbitrary” way employed for easier and better approach to an explanation,
            but in the end of the day simply addresses the energy “differential potential” or the “tension”
            in between the atmosphere and “hard” Earth, where even the part of “hard” Earth,
            its surface, that dynamically couples with atmosphere, still holds far far much more energy than atmosphere…
            which if thinking clearly, and considering it from this point, it means that you may reconsider that you may be “fatally” wrong about the “direction” of that
            “electricity potential flux””, where it, it could be the other way around…. where;
            the direction of that “flux” consisting as from Earth’s surface
            to the atmosphere.

            Maybe this just of no much value, but I think still very much helpful if considered.
            Every thing, exist and propagates, through the means of variation, in concept at least,
            I think…
            Where “positive” versus ” negative” simply arbitrary points of “approach” for an easier and better understanding… but still “arbitrary” anyway.

            (As a side bite…What is the actual direction of electricity in the means of a semiconductor;
            the directions as per consideration of “electrons” or as per that of
            “holes”?!)

            Thank you.

            cheers

  1. “We always thought that the bulge size and winding of the spiral arms were connected”, says Masters. “The new results suggest otherwise, and that has a big impact on our understanding of how galaxies develop their structure.”

    So, well-established, century-old scientific consensus was wrong. Imagine that!

  2. The first thing that comes to mind is the age of the galaxies.

    We are told that when you look farther away, you’re also looking farther back in time. link So, when you look at farther away, and therefore harder to see galaxies, you’re looking at younger galaxies. The easier to see, nearer galaxies are older. I wonder if they considered that.

    • So, when you look (from the earth) at farther away, and therefore harder to see galaxies, you’re looking at younger galaxies.

      Me thinks …… logical reasoning and intelligent deduction ……. will discredit the above assertion.

      But, …… iffen you were at the center of the universe doing your “looking”, … and you believe the “big bang” theory, … then the assertion is probably correct.

        • There is no “center of the universe” just as on the surface of an expanding balloon there is no single point of origin. Every point is moving away from the other, and the further away ((along the surface) the faster it is moving away.
          A balloon though is a 2-D sheet, whereas our observable universe is 3D physical dimensions. But the conceptualization is the smae, just imagining 3 physical dimensions expanding requires higher ordered math that Einstein has to teach himself.
          The radial dimension “r” in the expanding balloon conceptualization is time “t” in our universe.

          • There is no center of the universe.

            Now boys, …… I never stated there was a “center of the universe”, ….. I simply told commieBob that …… “iffen you were at the center of the universe doing your “looking””.

            But anyway, regardless of whether or not the universe is described as an expanding “flat disk” or an inflating “balloon”, ……… the structure still has a “center point” of origin. And ….. UH, that is, only iffen you ascribe to the “big bang” theory which I noted above.

            Iffen you are travelling on an Interstate highway, …… and you get a QUICK “look-see” at a car way behind you, …. and a car way ahead of you, …. and all 3 cars are moving between 60 and 100 mph, …. there is NO WAY that you can determine which vehicle started on its journey first ….. or how many linear inches separate each vehicle ……. unless you get help from the FSM.

            And if you think I am mistaken with my above reasoning, …… please correct me.

            I am a “student” of science, …….. not a mimic of consensus opinions or dictator of said.

      • All points of the universe are it’s “center” – expansion (supposedly) happened at all points in (nearly) the same way. (There had to be some differences to explain the current structure of the galactic web).

        I have never completely bought into this idea…I suspect expansion was not nearly uniform, but no evidence to support my hunch. The is a strange phenomenon called the “Great Attractor” where a stream of galaxy clusters seem to be headed towards might lend evidence – if its for real. The data is still somewhat ambiguous.

        • All points of the universe are it’s “center” – expansion (supposedly) happened at all points in (nearly) the same way. “. So the “Big Bang” happened equally at all points of the universe? That means that stuff was already equally distributed before the bang? So why is it expanding now, not just increasing its entropy (mixing)?

          That’s the trouble with having a Newtonian mind in a modern world – all questions no answers.

          • That’s the trouble with having a Newtonian mind in a modern world – all questions no answers.

            Thank you, Mike Jonas, ….. I really enjoyed that comment …… simply because it would be appropriate for most all disciplines at one time or another.

          • Yes, it happened at all points at the same time, because all points were the same point, or very nearly.

            That’s what makes it so fascinating.

          • Yes, “That means that stuff was already equally distributed before”

            as heat!

        • The “Great Attractor” is particularly suspect when the assumed Galactic Masses and kinetics just got blown up.

  3. I sincerely hope it will not take nearly a 100 years for scientists to overturn current scientific claims about climate change and impact.

    • There are only two factors likely to overturn these claims:
      1. The world demonstrably cools … although this will undoubtedly be represented as a totally unpredictable natural phenomenon that, thankfully, saved us from the otherwise inevitable anthropogenic Thermageddon that was just about to hit;
      and
      2. The drying up of funding available for this ‘science’. If there’s money to be had, scientists will go for it.

      • SL, you are not paying attention to the green blob.

        Everything that happens is ‘as predicted by climate scientists’ no matter what occurs.

        This way they are always correct.

        We need another Heracles to kill the many-headed Hydra of CAGW

  4. Hmm. So if the central understanding of galaxies is wrong, where does this leave dark matter? Dark matter was needed to explain galaxies as they were understood. That understanding has now changed.

    • This has no impact on the theory of dark matter.
      Dark matter is needed because the rate of spin of galaxies can’t be explained the amount of matter that we are able to observe. This discovery doesn’t touch on that.

      • Except we had been making a certain number of assumptions about the mass of the Galaxies and what the Spirals were. Those assumption just blew up.

      • MarkW
        June 12, 2019 at 6:44 am

        This has no impact on the theory of dark matter.
        ———————–

        Mark, I think you missing a very fundamental thing in the consideration of “dark matter”
        If we got to use a term like “initial condition” as per means of ‘dark matter” considered in cosmology, does not happen to be a theoretical or hypothetical one in substance.

        It consist as a discovery, due to application of science and the scientific method.
        The “proper” hypothetical development part comes later, as a means to try and explain this condition.

        So maybe you may reconsider that this, still has a great or even a grave impact towards the hypothetical guess, even where still no impact at the condition itself that still stands as a “discovery” as per merit, due to mainly, if me not wrong in this, Newtonian physics.

        And, if me still not that wrong, that hypothetical guess explanation still contradicts to the core the Newtonian physics, the very bases of the “discovery” of “dark matter”…
        very weird indeed, at least to me…

        Still, as far as I can tell, first comes the “discovery”, then the feverish hypothetical explanation attempt of it…or as I could put it other wise, the very and highly exotic feverish attempt on explaining it…with no much regard of fundamental contradictions there…
        hey, every thing goes and “ticks” within the means of the “highly exotic feverish” hypothetical guesses… no wonder there!
        Just how it is usually.

        cheers

      • MarkW – June 12, 2019 at 6:44 am

        This has no impact on the theory of dark matter.
        Dark matter is needed because the …… yada, yada

        MarkW, ….. me thinks that “dark matter” is nothing more than an astronomer’s “CYA”.

        Iffen the universe is full of “dark matter”, …….. and that “dark matter” has mass, along with a gravitational “attraction”, ……. then how is it possible that the “circular” trajectories of Periodic Comets, …… like Haley’s, …… is unaffected on its 78 years of travels through our galaxy?

        Unless of course, maybe the Periodic Comets are unaffected by gravitational “attraction”.

        • Describing Haley’s Comet (or any of the others) “travels through our galaxy” is like talking about the flea on your dogs back travels through our solar system…. except the scale is even larger. So no, dark matter wouldn’t be expected to materially change its course. Either it’s localized, in which case it far enough to treat as point sources like other stars, or is diffuse enough that it applies equally everywhere, and we just don’t know how to look for it.

          • or is diffuse enough that it applies equally everywhere, and we just don’t know how to look for it.

            Then wouldn’t the comet be colliding with the “dark matter” …… and “sparks” would be flying every which way?

          • Check out the history of measuring the speed of light in the late 19th century. Physicists were convinced there was an “aether” that was the medium through which light (and E&M in general) propagated. It had the really weird properties of being unmeasurable and producing no drag on the planets and stars and such, but yet stiffer than steel, stiff enough to let light waves ring through at 3 X 10^10 cm/sec. People were actually expecting to see the heat (sparks?) from comets and planets as they plowed through the aether.

            It was unmeasurable, because it *was not there*, as the Michelson-Morley experiment showed. The theory and accepted norms of institutionalized Newtonian Physics (but not Sir Isaac himself! He was on the right track concerning light!) were wrong. This was the beginning of the paradigm shift to “modern” physics.

            Dark Matter is unmeasurable because it is not there; it is a made-up travesty of a wild invention that is created to explain an observation that “current understanding” can’t square up. There is a problem with either theory or measurement.

            We just found a major hole in the “accepted measurements”.

          • it is a made-up travesty of a wild invention that is created to explain an observation that “current understanding” can’t square up.

            MST, ….. my thoughts the same, ….. that is why I told MarkW this in my above post, to wit:

            ….. me thinks that “dark matter” is nothing more than an astronomer’s “CYA”.

    • Dark matter is needed to explain the rotation speeds of stars at various distances from the center of a galaxy, but I haven’t seen it used to explain the actual “structure”.

      Spiral arms are what if not pressure induced waves acting on gas clouds? There is not enough gravity to hold one together from smearing out due to rotation around the galactic core.

      A spiral bar??? How the heck do you get a static appearing object (made of stars) rotating around the center of the galaxy? It would have to be an effect of how energy is leaving the central black hole, but the angular momentum seems wrong (one would expect the poles of the black hole to be up and down, not sideways). (Maybe is takes two black holes to produce a bar?)

      • Robert, I agree. Dark matter solves one problem only to create a dozen more. like ghosts, I can’t see them, they don’t bother me, I can’t interact with it, I’ll just pretend it doesn’t exist…
        People try to apply SolarSystem orbital mechanics to an entire galaxy, as if all stars rotate around a center mass. In truth, it’s the combined mass of the entire galaxy pulling against fast moving stars on the edge that keeps it in check. Stars at the center move slowly because they’re pulled equally in all directions. This balance causes the galaxy to rotate at the same speed like a record disk.
        For instance look at irregular galaxies which are nothing but a cloud looking blob. They do not rotate so much as oscillating through the central mass. Slower stars move very little, the faster ones will pass through the central mass to the far side before the pull of gravity tugs them back in. No dark matter needed.
        The discovery of “faint galaxies” show the absence of a central star cluster causes a loose, larger galaxy that moves very slowly. It is said these are examples of galaxies with no dark matter in them.
        A theory on bar galaxies is that two galaxies collided with the center masses orbiting each other. Two massive black holes may fit the model better. More data is needed.
        As for no correlation between the center mass in the spiral arms, I am glad they are adjusting the theory to fit actual observations. The most consistent thing through the universe is balance. One spiral arm will match another on the opposite side, if it’s disrupted by colliding galaxy the whole thing falls apart… Before falling back together.
        Now for a little heresy… It appears that gravity is a force like magnetism that occurs instantly, not at the speed of light. Otherwise, none of the outer stars can be attracted to a central mass 70,000 light years in the past location. Everything would unravel.

        • Max,

          “Now for a little heresy… It appears that gravity is a force like magnetism that occurs instantly, not at the speed of light. Otherwise, none of the outer stars can be attracted to a central mass 70,000 light years in the past location. Everything would unravel.”

          Since gravity is not a force but a bending of space/time due to the existence of matter, it is not subject to the C speed limit. It is more of a ‘concept’ like the movement of the intersection of the two blades of a pair of scissors which is not constrained by the speed of light.

          • In the quantum world C is not a speed limit. See the Delft study regarding quantum entanglement.

          • Since gravity is not a force but a bending of space/time due to the existence of matter, it is not subject to …………..

            OK, ……. so iffen I step off of the top edge of a 20 story building, …… my descent to the ground below is nothing more than ….. “a bending of space/time”?

            Interesting. …… Verrillllley interesting.

    • Bible says that the seemingly improbable way the universe hangs together, with insufficient mass, is Jesus:
      Colossians 1:17: “He is before all things, and in him all things hold together.”

      This doesn’t make too much sense until you take Astronomy class and the instructor tells you that there should be 90% more mass in the universe, and we cannot “find” it, so we give the missing mass a name and declare it exists. Like the Oort Cloud.

  5. I have always wondered if there is a bias towards right or left spin in spiral galaxies. Do globular galaxies have spin?

  6. This is more than interesting: It is fundamental. You just witnessed the torpedoing of a great deal of the crock of theory that is the Dark Matter ship.

    There is circular logic that went: Central Bulge Massive > Tight Wound Spirals. Therefore Tight-Wound Spirals > Massive Central Bulge. And then since the mass calculations the orbits of other galaxies associated with those is thrown off, and so on. The Dominoes fall. The largest difficulty in Celestial Mechanics is the “wrong” speed of orbits of outlying stars in galaxies. Galaxies “should” fly apart. Dark matter was invoked to “fix” that. If we have been guesstimating the mass of the Galaxies completely wrong to begin with, Dark Matter is a solution with no problem, or even more difficult to understand if there has to be even more of it. If the cause of Spiral arms is not relatively static density waves, then we don’t have any idea how fast the stars in the arms “should” be going. Etc., etc.

    Boom! Bye-bye Dark Matter (as theorized for the last 40 years, anyway.) The ship sailed and is sunk. Good luck refloating it.

  7. Here we go again –“state-of-the art computer models”. So the fundamentals of galaxy formation/structure can be murky (ref: dark matter), and but they insist they have “state-of-the art computer models”?

    • I understand your skepticism, because the assumptions necessary to drop Navier-Stokes into a computer are humongous, but here we are just looking at a two-variable statistical correlation: Tightness of spiral arms, vs. Mass of central core. Is there a trend? Y/N?

      No.

      *Not* the answer they were expecting, so at least they are honest in reporting the results and actually trust their assumptions, even if they *did* screw up the programming, which I doubt. They just cut off a big limb the profession had been standing on for a long time.

  8. I think those posting sarcastic remarks are confusing astronomy, which is searching for answers to questions, with climatology which is searching for anything that would validate their re-determined answers.

  9. Dark matter is a lot like CC, something we don’t know much about, so lets
    call it something, problem solved..

    I still think that Hoyles “Strady State”is far more likely than the ”
    Big Bang”” theory. Time of course will tell, but its a big bit of time.

    MJE VK5ELL

    • I’m sure someone has calculated the greenhouse effect of Dark Matte, and the Charney sensitivity. Hey all that Dark Matter should be keeping a galaxy snugly warm! Maybe there is even feedback of Dark Matter turbulence?

  10. Applying Kepler’s 3 laws to a galaxy is a simply daft – they apply to solar systems.
    What is the difference one might ask?
    Solar systems have >90% mass at the star and a little bit in all the planetoids around.

    Our galaxy has a 4 million solar-mass central object , but a 300 billion solar-mass disk including arms.
    M87* (of EHT fame) has a 6 billion solar-mass central object but a trillion solar-mass fat disk.

    So applying Kepler’s laws to galaxies is nuts. They then come running to CERN who say no detector sees any trace of “dark matter”, no matter how much tax money is accelerated. Who programmed the models, I wonder? Climateers?

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