It's a Dusty Universe Out There

By Sean Carroll | March 17, 2010 8:25 am

The primary goal of the European Space Agency’s Planck satellite is to provide a map of the cosmic microwave background with unprecedented precision. But along the way, you have to take into account that there is stuff in between us and the farthest edges of the universe — in particular, there’s all sorts of dust here in our home galaxy. You can even become famous just studying dust; one of the most highly cited papers in all of astrophysics is a 1997 map of galactic dust.

Dust isn’t only an annoyance — it’s also pretty. Planck hasn’t released any data about the CMB yet, but they just released a map of the cold dust in our local vicinity, looking for all the world like an abstract expressionist painting. (I want to suggest a particular artist, but my mind is blanking.) Click to embiggen.


It’s a false-color image, of course; the dust is very cold (tens of degrees above absolute zero), and the image is constructed from microwaves, not from visible light. You can see the plane of the galaxy, and the filamentary structures arising from all the churning of the interstellar medium from supernovae, star formation, magnetic fields, and so on.

Okay, pretty time is over. Let’s see the CMB.

  • Will

    Looks like a Turner to me. Not an expressionist, of course.

  • Sean

    I think you’re right, that’s a better association. Can almost see the ships in the background.

  • Low Math, Meekly Interacting

    Any particular areas of interest besides CMB backgrounds that this data might inform? Galactic evolution and dynamics? Stellar evolution? More local maps of dark matter, maybe? Etc.?

  • NewEnglandBob


    I see horsies!

    Ride of the Valkyrie.

  • NoJoy

    Looks like Hell to me. My link didn’t work, but a google image seach for Hello Kitty Hell yields a hilarious image that would look great superimposed on this.

  • Jason Dick

    I’m really glad they decided to release one of these images :) When I first saw these a little while ago, I thought they were truly exceptional. I believe it was Stewart Lowe who compiled the images, with the basic idea being, “If the human eye could see three microwave frequencies, instead of red, green and blue, what would it look like?” These images are the result, and it is simply stunning, at least in my opinion.

  • Stuart

    Jason, unfortunately I can’t take credit for this one :-)

  • Jason Dick

    Ah, sorry Stuart. Sorry I got your name wrong too :(

  • per


    I have a beginners question. The current standard model of cosmology more or less fits all the observed properties of lensing, cmb, supernova etc correctly right? However, have it made any predictions that later has been verified by experiement? Or is it only to be viewed as a best fit candidate?

    cheers, Per

  • sarah

    oh sean, you do such a good job of sounding like a cosmologist — making it sound like dust is either annoying or pretty, but not in the “scientifically interesting” category…. 😉 while SFD97 is highly cited because it is super, super useful, there are loads of papers about dust itself… and you can’t understand star or planet formation without understanding it!

  • Sean

    I was wondering when someone would complain that I wasn’t giving dust its due. Don’t worry, I do appreciate that the interstellar medium is interesting in its own right! My Ph.D. advisor did work on it for much of his life, after all.

    per, the standard model has made lots of predictions that later came true, starting with primordial nucleosynthesis and the CMB itself. If you mean more particularly the ideas of dark matter and dark energy, the answer is still yes — they made predictions about the CMB, growth of structure, baryon acoustic oscillations, etc.

  • Lab Lemming

    We are highly processed dust, as is the planet we live on, so don’t bag it. That picture isn’t just pretty, it is a distant family photo.

  • Sean

    Via NoJoy, here is Hello Kitty, in Hell, as portrayed by interstellar dust.

  • Brian137

    Inflation should lead to a flat universe. At the time the theory of inflation was introduced (1980 or so) we had no idea whether this condition of flatness would hold, but our latest data suggests that it does. Flatness is a “just so” condition, requiring very tight bounds on the parameters, and so seems (to me) unlikely to have occurred by coincidence.

  • Matthew

    It should be noted that of the three wavelengths that went into this image, two came from Planck (540um and 350um) and the third from IRAS (100um), a satellite which mapped the sky in the early 1980s. The IRAS contribution alone can be seen in this image.

  • Pieter Kok

    It is worth clicking on the IRAS image, because it gives a good indication of the size of the area that is covered.

  • Brian Too

    Oh c’mon, it’s clearly a Pollock. I can see where he dripped the paint!

  • Matthew Pollard

    Remarkably similar:

    This Turner

  • Ellipsis

    perhaps Gerhard Richter or Sigmar Polke

  • Eric

    Low Math @3:
    In addition to Sarah’s points at 10, dust is a pretty good tracer for the gas whence comes the diffuse gamma ray emission seen by, for example, Fermi. The better understanding we have of that diffuse background, the more we can learn about the rest of the stuff in the galaxy. Not that the diffuse emission isn’t interesting on its own.

  • Peter Erwin

    Those of us who actually cite the Schlegel et al. dust paper Sean refers to know it’s from 1998, not 1997 … 😉

  • spaceman

    Dear Sean,

    first of all, beautiful picture of the galaxy’s dust. However, beautiful as it is, does all of this dust not bode well for Planck’s prospects for seeing a clear view of the CMB fluctuations?

  • Sean

    Dust is an important foreground that must be taken into consideration when observing the CMB, no doubt. The good news is that dust affects different wavelengths in different ways, so to a large extent it can be removed (that’s a major purpose of maps like these). But often when people analyze the CMB sky they simply remove the regions where dust is too severe.

  • Pingback: From dust to stars | Cosmic Variance | Discover Magazine()


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Cosmic Variance

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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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