The darkness and the light

By Phil Plait | May 9, 2012 6:32 am

The sky is not as it seems.

Certainly, gazing upon it on a clear night you see so much: stars, planets, the glow of hot gas here and there… but there’s also darkness. Look at the Milky Way, its stream split down the middle by a rift of black. Gape at a gaudy nebula, and you’ll see it pocked here and there by pools of black.

But what is inky pitch to our eyes glows with a cold light to those attuned to it.

Tell me, what do you see here?

The bright star is obvious enough, but you can also, dimly, see a feathered stripe of black splashed across the vista, blocking, absorbing the light from stars behind it. Details are muted, structure difficult to ascertain, and you strain to see features that your brain cannot interpret.

But that’s with your eyes. Try again, look at it, but this time, widen your view. See it now?

Well done! Where before you saw material absorbing light, now it emits! Of course, unbeknownst to you, you had some help: the ESO APEX telescope in Chile. It sees into the far, far infrared, where light is so stretched out it is entirely invisible to humans. In fact, the wavelength of light is so wide there that if it were a vibrating string, you could physically see the crests and troughs, since each would be separated by the next by nearly a millimeter. The light your eye can see has a wavelength only a thousandth that wide.

When APEX looked at this ribbon of dark, frigidly cold dust, it sees the material glowing. What we see as dark, it sees as bright. You can even compare the two directly, using a slider over the two versions of this picture, unveiling precisely what your now-expanded vision can take in.

Cold dust is the bane of the astronomer who uses merely visible light, since it blocks the view behind it. But one person’s poison is another’s meat, and if you study the material that wends its way between the stars — and sometimes comes together to form them — then the view from APEX is sustenance for you. This material is barely above the ultimate freezing point of absolute zero, and you might think it dead and useless. But from such stuff are you and I descended, and everything you see around you.

So when you do peer around you, and take in your environment, your surroundings, your home, look again. You are surrounded by the invisible, permeated by it… but always remember, it was invisible only until we chose to look for it. We created the means necessary to do so, and when we did the Universe opened up before us.

Image credit: ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin.


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Comments (16)

  1. Other Paul

    Oo-er. Isn’t that the Nexus Ribbon?

  2. Michael Simmons

    How far towards forming a stars are the three brighter clumps just left of middle on the strand of dust?

    Is it possible to take a far, far infrared spectrum to find out the composition of the clouds?
    If so can velocities within the cloud be measured by the Doppler shift within the spectrum?

    Can anything be inferred about the dark matter with in the clouds? Perhaps using velocity information.

  3. Chris

    @1 Other Paul

    Darn, you beat me to it! Cosmic String was my other guess

  4. Tom K

    “So when you do peer around you, and take in your environment, your surroundings, your home, look again. You are surrounded by the invisible, permeated by it… but always remember, it was invisible only until we chose to look for it. We created the means necessary to do so, and when we did the Universe opened up before us.”

    That sounds like something the woo-woos would say.

  5. Dan Batcheldor

    @Michael:
    The 3 blobs you point out might actually be stars, or at least proto-stars (stars in the process of forming).

    IR spectra of the clouds have been collected. The dust in the interstellar medium is generally made up of heavier elements (so called “metals”) processed in the core of now dead stars. This previous generation of stars kindly redistributed their metallic remains via a nebulous phase, before becoming white dwarfs. The chemical composition of the dust varies, but is typically some form of silicon, carbon and more complex molecules (including water ice). The spectrum would indeed give you a measure of the velocity of the clouds (along our line-of-sight), and of the dispersion of the velocities within the clouds/your spatial resolution.

    The effects of dark matter are seen on scales much larger than individual dust clouds, so we typically use velocity information from gas (hydrogen) distributed through the entire galaxy (and other galaxies) to infer its presence. If you are wondering, the collapse of the clouds into new stars is triggered by small fluctuations in the densities of the clouds (not related to dark matter), or by some external process (say the passing of another star, the shockwave from a nova, or the collision of two clouds).

  6. arabwhipmonk

    Isn’t the temperature of the material found from the temperature of the emission? This low value doesn’t correspond to the temperature in the star forming regions in the dark dust clouds, right?

  7. Russell

    There’s that “dust” again. Where does that much dust come from…its pretty dusty in space.
    I saw the web page that had a microscopic view of space dust and a description of it, that it may be reddish color or other depending on what it is made of. It was collected form our solar system. Ok that makes sense because we have planets, asteroids and such flying around here.

    Now I am wondering where all this dust comes from way out there in the middle of nowhere??? That much! How did it all get there?

  8. John

    @8 Russell:
    There are a few ways you can get that dust, but often if there’s that much of it you’re looking at the remains of old, dead stars. Some stars collapse when they get too old to keep burning, but others explode. If they explode, they blow out heavy elements which, if gravity does what gravity does, can eventually get all pulled into a ball and ignite, creating a new star. If that’s what created this dust (and it’s certainly possible that that’s the cause) then you know it didn’t come from out solar system – it came from one far, far away in both space and time.

    I don’t know how you feel about Wikipedia as a resource, but I find it pretty spot on for pure academics. If you’re interested in learning more about that process (and others that could create so much dust out in space) start with the page on “Stellar evolution” and click on through. There’s a lot of good, fascinating stuff, and many of the sources cited are free to access.

  9. arcblast

    Wow! I love how your presentation of the images has just as much impact as the photos themselves! I had to go back and read it aloud! Well done, sir!

  10. Slam1263

    Dude.

    Dude.

    Dude, I am so high right now, I can see near-infared, and x-rays.

  11. “So when you do peer around you, and take in your environment, your surroundings, your home, look again. You are surrounded by the invisible, permeated by it… but always remember, it was invisible only until we chose to look for it. We created the means necessary to do so, and when we did the Universe opened up before us.”

    Wonderful writing. Made my day to read it.

  12. Michael Simmons

    @arabwhipmonk

    I initially assumes the same.
    Perhaps the cloud is so dense that a stars energy is being blocked and we can only see the faint heating of the surrounding cloud that makes it out.

    @ Dan Batcheldor
    Thank you

    I think a huge amount of information could be gathered from a false colour image of the cloud showing blue for the parts moving towards use and red for those moving away.

    A few more questions.
    What would be the effect of a black hole passing though the cloud? Could it be detected in the Xray region? if so could the cloud be used to constrain the density of black holes in the region of the cloud?

    What is the size of this cloud?

    What would the passage of a normal star though this cloud look like?

    The structures in the cloud to the right almost look like holes punched though the cloud.

  13. wodun

    Huh, imagine that. Things exist that we cannot perceive with our senses. This is certainly a reminder that so much exists outside our perceptions.

  14. Who wrote this? It’s brilliant!

    /came her from fark.com

  15. JB of Brisbane

    @Chris #3 – “No, that’s a completely different phenomenon.” – Miles O’Brien.

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