Cold fire threads Orion's Belt

By Phil Plait | May 2, 2012 6:00 am

Orion is the gift that keeps on giving. When you look toward that constellation in the sky, you’re facing a region of massive ongoing star formation. A sprawling cloud of gas and dust occupies Orion’s midsection, most of it thick and opaque. Some of it is illuminated by stars embedded inside, and some by the reflected light of nearby stars.

M78 is a section of the cloud just above Orion’s Belt that’s evidence of the latter. But even then, much of the dust is dark to our eyes. But if you look in the far, far infrared, where warm material glows, a different — and spectacular — view appears:

[Click to blackbodyenate, or grab the 2300 x 3500 pixel version.]

This is actually a combination of two views: one in visible light from the Digitized Sky Survey, and the other from the APEX telescope, which can see light in the submillimeter wavelength range — 1000 times the wavelength the human eye can see. Only cold, cold objects emit at this wavelength, things a few degrees above absolute zero.

The blue material in the image is gas and dust reflecting starlight from nearby blue stars, so it can be seen in visible light. The cold dust, though, threads in front and behind the visible material, and can only be seen by APEX’s eye, tuned as it is to the far infrared. Falsely colored in this image, it glows an eerie orange like fire running through cracks in the nebula.

But it turns out the cracks are the fire itself…

The inset image here is from my friend Travis Rector. It covers roughly the top 2/3 of the picture above, but shows only the light that we can see with our eyes. You can see that where the cold dust glows in the APEX image, it appears dark here. Thick cold dust absorbs visible light, so it appears dark to our eyes. In astronomy, what looks bright and what looks dark depends very strongly on how you look at it.

But there’s more to this story, too. That thick dust is actually shrouding a nursery! Buried deep in that cocoon are stars that are forming — you can see them as bright knots in the orange APEX image. M78 is known to house quite a few young stars, several dozen, some only a few million years old. Using just visible light telescopes we’d only see those stars that are out in the open, while the others swaddled in that blanket of dust would remain invisible. Using APEX, they pop out like embers in a dark fireplace.

It’s always fun to be reminded that we see only a narrow, narrow slice of the Universe with our eyes. But we’ve extended our vision across the spectrum, enhancing and expanding our view. The Universe glows fiercely everywhere we look, and places we once thought dark are actually ablaze with new light.

Image credits: ESO/APEX (MPIfR/ESO/OSO)/T. Stanke et al./Igor Chekalin/Digitized Sky Survey 2; Travis Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF)

Related Posts:

Rudolph the red-dusted Strömgren sphere
Desktop Project Part 18: X-raying the Pac-Man nebula
The gorgeous birth pangs of young stars
The cold, thin, glorious line of star birth

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: APEX, dust, M78, Orion, star formation

Comments (10)

  1. Junior

    Speaking of wavelengths, as a kid I often tried to imagine what would the world look like if we had “radio-wavelength” goggles. I imagine the walls and people to be semitransparent and the far beacons of radio-station towers glowing fiercely in the distance. That would be an interesting gadget to build.

  2. Pete Jackson

    Great images! I notice that there are still significant dark areas around the visible nebulosity where no stars are showing, indicating that there is cold dust there, but are also not showing on the APEX image as well. I downloaded the combined image and cranked up the gamma on Microsoft Photo Editor to see if there were any enhancements in those areas above the sky background, and there were still some totally dark areas. I don’t know what is APEX’s sensitivity to very cold dust, but these superdark areas may represent dust cooled down to just a few Kelvins above absolute zero, i.e. down close to the 3 K temperature of the cosmic microwave background.

  3. Eric

    I always wonder how big nebulae are. How far apart are the top left edge and bottom right edge of this cloud?

  4. @ Eric: Looks to be a couple of inches.

  5. Jon Hanford

    @#1 Pete Jackson,

    I noticed while reading the ESO press release at the site that APEX submillimeter observations only includes a portion of this image, not the entire field, as seen here:

    That said, some areas still appear dark at both submillimeter and visible wavelengths. Must be quite cold there.

  6. Jim Moore

    Why are stars forming like pearls on a string in these rivers of dust?

    Does this shed any light on how stars form?

  7. Steve Metzler

    @Andrew (#4):

    I see you’re not the only former class clown that hangs out here.

    But srsly, though it is a composite, that is one of the most spectacular images the BA has ever posted here. I’m going straightaway to get the large image, and turn part of it into a desktop.

  8. The (slightly) warmed dust reminds of me a mantis. :) Pareidolia at its best!

  9. The (slightly) warmed dust reminds me of a mantis. :) Pareidolia at its best!

  10. @7, Steve: that would be awesome.

    Imagine each morning sitting at a desk that has this nebulae-formation on top of it…

    *snort* *giggle*

    Seriously, I don’t understand why this image is “spectacular”. We can’t see in the infrared so this isn’t spectacular. It’s basically a painting. If you use pink as the color that represents infrared, it would look ridiculous. Just because the researchers chose orange/yellow it’s considered “spectacular”? I don’t think so. I think it’s beautiful, yes, but just last month the BA posted that sideways look on the milky-way spanning 200 megapixels or whatever it was.

    So you better watch your superlatives ūüėČ


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