Behold the stereo awesomeness of this rotating nebula

The moon surrounded by a lunar halo with Jupiter (right edge of halo) and stars. All these celestial objects are too far for our eyes to sense which is closer and which is farther. They might as well all be at the same distance. Of course we know they’re not. Photo: Bob King

Outer space is so 2-D. Or so it seems that way to our eyes. Look up at the moon or the planet Jupiter tonight and there’s no way to sense they’re any closer than a star 100 light years away. The sky has no depth.

Our brains build a stereo, 3-D picture of the world based on two separate images from our eyes located on opposite sides of our face. We see the world with binocular vision, but it fails us when objects are too far away to look any different from either eye’s perspective.

Red-cyan 3D glasses.

When it comes to the sky, we’re hopeless at sensing depth and estimating distance. If we could enlarge the distance between our eyeballs to several hundred million miles, they’d be useless for nearby viewing, but we’d begin to see the planets and closest stars in true stereo. Our current pair is simply too close together to provide a baseline long enough to see an object from two different perspectives across the vast distances of outer space.

A rocking motion of the moon called libration lets us see it from different perspectives during its orbit of Earth. Two photos of the moon taken months apart were combined in this anaglyph image for a wonderful 3D view. All you need is a pair of red-cyan glasses to see it. Credit: Vladimir Jovanovic

Various forms of artifice have been invented to trick the eye into seeing the universe stereoscopically including those cool, anaglyph “movie glasses” that show slightly different images of a scene to each eye by means of color filters. One version of the scene comes through the red filter, the other through cyan.

Our brain combines the two views into a realistic stereo image. The only drawback is that they work best on black and white scenes. For color viewing of movies, polarized glasses are used to the same effect. Click HERE for a nice explainer of how each works.

The nebula IC 1396 is a large cloud of gas and dust called an emission nebula. It’s 2400 light years away and set to glow by the white star seen near center. The nebula spans 3 degrees or six full moons in the sky. Click for 3D animated view. Details: 300mm f/2.8 telephoto, total exposure ~5 hours. Credit: J-P Metsävainio

Finnish astrophotographer J-P Metsävainio took things a step further when he created a lovely 3-D animation of the distant nebula IC 1396 in the constellation Cepheus. Using a technique called lenticular printing he took the original photo and made two dozen separate views from slightly different angles based on basic assumptions about the structure of the nebula.

A nebula’s central star typically both illuminates and hollows out a cavity in the dense gas around it by the emission of strong ultraviolet radiation. That’s the inner blue region. Those dark blobs and streaks are likely in the foreground since they absorb light coming from behind. Their streamlined shapes tell us that radiation from the star is stripping material away like a leaf blower blasting through a pile of leaves.

Based on these assumptions and creative artistry to fill in the gaps, Metsävainio assembled his photos into a good guess of how this spectacular cloud would look if we could see it in three-dimensional glory. I’d post the animation here but the file is 7MB, way past my size limit. Click the photo for the pleasure and take a few minutes to check out more Metsävainio’s work HERE.

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