This ‘Ghost Galaxy’ Is 99.99% Dark Matter

By Ryan F. Mandelbaum | August 25, 2016 1:42 pm


The hazy oval isn’t glare on your screen; it’s an entire galaxy. Dragonfly 44 weighs about the same as our Milky Way, except it’s 99.99 percent dark matter and has less than a hundredth the number of stars. Dark matter is stuff that can’t interact with the electromagnetic force (how we mostly experience the world) so we can’t see or touch it.

Scientists can observe its gravitational effects, though, which keep Dragonfly 44’s paltry collection of visible stars from flying apart. There’s around five times as much dark matter as regular matter in the universe, and even our own Milky Way is around 90% dark matter.

Astronomers found Dragonfly 44 with the W. M. Keck Observatory and the Gemini North telescope on Mauna Kea, Hawaii and are publishing their results in The Astrophysical Journal. The team measured Dragonfly 44’s mass by observing its stars’ velocities as they zoomed around the galaxy.

In a press release, scientist Pieter van Dokkum from Yale University pointed out that a galaxy like this one would allow astronomers to better study a huge mass of dark matter with far fewer stars to block the view, or lack thereof.


This article originally appeared in

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  • joseph2237

    And you know this how? Please tell the Noble Academy that you have a Black Matter detector. They have an award all made out, they are just waiting for a name to put on it.

    • Andrew

      Lol do you even science? And wtf is Black Matter?
      They have a special Darwin Award waiting just for you…

    • StuartLondon

      You observe the orbit of stars etc. To calculate gravitational effect, then minus visible mass and what you’re left with is dark matter.

  • Uncle Al

    Visible mass does not account for the galaxy’s orbital dynamics. Saying “dark matter” is as disingenuous as saying the Pioneer anomaly is proof of non-classical gravitation or a Fifth Force. For something that is “90% dark matter,” the Milky Way ivery coy about having it be detected as such.

    The Tully-Fisher relation is universally modeled by Milgrom acceleration with zero wiggle room. Milgrom acceleration is sourced by Noetherian leakage of angular momentum conservation given trace chiral anisotropy of spacetime that also sources baryogenesis. Trace chiral anisotropy of spacetime is directly quantifiable in desk top apparatus. It is specifically excluded from physics By Green’s function (never validated within General Relativity). Don’t postulate, measure – then stop whining about anomalies.

  • Charlie Currie

    Those apparent gravitational effects are thermodynamic causal functions of displacement.

  • OWilson

    Interesting stuff, but they haven’t a clue what a Big Bang is, what matter is, or space is, or what Dark Matter is, or what Dark Energy is, or how many Higgs-like particles (The God Particle) are out there.

    If you could track the actual activity going on in a cubic foot of space in front of you, there would never be a computer in the world to break down and track all that activity.

    I get tired of these TV types explaining everything to us, as if it were the revealed truth.

    Takes away the human awe and wonder, not to mention the fun questioning the “revealed truth”.

    We are no closer to understanding the nature of life and the universe than were the ancients. Sometimes folks forget that!

    Science is getting more like religion every day!

    • Uncle Al

      The Pioneer anomaly is Phong shading – anisotropic emission of infrared photons from its Pu-238 thermoelectric power supply: arXiv 1103.5222, 1107.2886. The latter is verification. The very small acceleration anomaly is decreasing in lockstep with Pu-238 half-life.

      • OWilson

        Ya ya we know, perfesser!

        Actually we don’t know, we are just told, and, as folks ask me all the time, who are YOU to questiion the revealed truth?

        So, sorry for mentioning it! :)

    • Robert Jackson

      You’d probably benefit from actually reading about physics. Until you do, your criticisms are uninformed and pointless.

      • OWilson

        I’m glad that’s settled, then!

        You have varying mathematical explanations that appear to fit some of your “observed phenomona”, (for the moment)

        Supersymmetry, string theory, multiverses, extra dimensions, branes, big bangs are all attempts at mathematical explanations. Most fail.

        Did you know the LHC at CERN publishes results only by “consensus” of more than 3,000 international, and competitive Nobel seeking “collaborators”, before a paper is published.

        Minority opinion (think Galileo, Einstein, Darwin), doesn’t fare very well unless you are also good a politics, and getting funding.

        The two main experiments, that are supposed to confirm the results, ATLAS and CMS, are supposed to be kept separate, but as one insider physicist notes, with a laugh, “Are you kidding?” Half of ATLAS is sleeping with half of CMS” :)

        This, post Higgs:

        “We are struggling to find clear indications that can point us in the right direction. Some people see in this state of crisis a source of frustration. I see a source of excitement because new ideas have always thrived in moments of crisis.” – Gian Giudice, head of the Theory Department at CERN”

        • Robert Jackson

          The standard model predicts 8 different Higgs fields so it’s not surprising if more types precipitate out of collider events. As for the qualifications of any statements regarding the one found, that is a common cautionary reflex among experimental physicists. They, like you, are rightfully skeptical of purely mathematical “theories”, which are more correctly regarded as hypotheses. But it is sometimes an unfortunate reflex, as in this case. We are talking about 5-sigma events, which are as close as we can come to certainty in any experimental observation. The Higgs has arrived and it will remain whatever else we find.
          As for the quote you referred to, the “crisis” discussed probably refers to the utter absence of SUSY particles in the data thus far; personally, I am very skeptical of string “theory”, and suspect the final extension of the standard model (the “Theory of Everything”) will not require SUSY, at least not as regards current 14 TEV capability. Oh, and I’m not a “queen” of any description, though I may have a disused blog site somewhere.

          • OWilson

            It was your apparent arrogant dismissal of my 60 years of reading science, that precipitated my less than gracious response. :)

            But no matter, your newer post shows you are capable of civilized discourse sans the dreary intellectually bankrupt responses I often get from the liberal side of things. :)

            The current state of the Standard model, as presently understood is in theoretical crisis, as our erstwhile Head of CERN above opines.

            I am deeply interested in humankind’s quest for understanding.

            My contempt is directed at those who point to science as settled, and use it for political or economic gain.

            They are never actually scientists, Obama, Al Gore, Leonardo di Caprio, Lady Ga Ga, Heinz-Kerry and so on.

  • Friz Martin

    I wonder if we may someday discover that the influence we call dark matter is actually the result of an unknown property of gravity.

    Perhaps the greater, denser gravitational forces near the center are channeled and more connected to the periphery of the galaxy than we recognize. Not so much a new force as an unrealized extension of the force of gravity.

    Don’t know, just thought I’d toss that out.

    • OWilson

      Your guess is as good as the guy on T.V., Bill Nye.

      But he get’s paid by PBS, and you don’t!

      • Friz Martin

        It’s a lot more interesting when you do it for free I find.

        • OWilson

          More open minded too. You can keep up to date!

          Once you’ve been on TV and told the great unwashed exactly what your “settled science” says about everything, you’ll defend it to the death.

          Either way, you are a fool.

          (see climate science)

  • OWilson

    “Scientists can observe its gravitational effects, though,”

    The ape hadn’t a clue what gravity was, but every time he fell out of a tree, like a scientist “he felt its effect”.

    Fast forward a million years, the Greeks pondered why thing fall. “Gravity?” opined some wag. “What is Gravity?” someone asks. “Look it up, its “the force that pulls”.

    Fast forward 2,500 years, now he’s managed to measure actually how fast he falls.

  • joseph2237

    Doesn’t look like the same cluster to me. Surrounding galaxies don’t match up correctly.

  • Lord Humungus

    LOL, dark matter is becoming a total joke.



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