Mostly Mute Monday: The Beauty Of Reflection Nebulae (Synopsis)

“Life is a mirror and will reflect back to the thinker what he thinks into it.” -Ernest Holmes

When you've got a gas cloud in space that emits light, it's only for one of two reasons:

  • Either it's at high enough temperatures that its atoms are excited and it's emitting its own light as the electrons fall in energy and recombine with nuclei,
  • Or it's cool and neutral, and is reflecting light off of the brightest stars in its vicinity.

That latter case has a dead giveaway: it always shines blue.

Image credit: ESO/Igor Chekalin, via Image credit: ESO/Igor Chekalin, via

But there's much more to these reflection nebulae than their color, there's also some amazing astrophysics at play, something we reveal when we look in infrared light and also at the dust lanes that obscure our view.

Image credit: NASA/JPL-Caltech, from the Spitzer Space Telescope. Best known as Messier 78, the two round greenish nebulae are actually cavities carved out of the surrounding dark dust clouds. The extended dust is mostly dark, even to Spitzer's view, but the edges show up in mid-wavelength infrared light as glowing red frames surrounding the bright interiors. Messier 78 is easily seen in small telescopes to the naked eye in the constellation of Orion, just to the northeast of Orion's belt, but looks strikingly different, with dominant, dark swaths of dust. Spitzer's infrared eyes penetrate this dust, revealing the glowing interior of the nebulae. The light from young, newborn stars are starting to carve out cavities within the dust, and eventually, this will become a larger nebula like the "green ring" imaged by Spitzer A string of baby stars that have yet to burn their way through their natal shells can be seen as red pinpoints on the outside of the nebula. Eventually these will blossom into their own glowing balls, turning this two-eyed eyeglass into a many-eyed monster of a nebula. This is a three-color composite that shows infrared observations from two Spitzer instruments. Blue represents 3.6- and 4.5-micron light and green shows light of 5.8 and 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer. Image credit: NASA/JPL-Caltech, from the Spitzer Space Telescope.

Come find out the full story -- with some glorious, high-resolution images -- on today's Mostly Mute Monday!

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