Look Into the Cat’s Eye…

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Are you ready for more stereo vision? This haunting Hubble Telescope image has been visualized for dimension by the one and only Jukka Metsavainio and gives us a look at one of the most complex planetary nebulae ever photographed. Inside NGC 6543 – nicknamed the “Cat’s Eye Nebula” – the Hubble has revealed delicate structures including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas… and thanks to Jukka’s “magic vision” we’re able to take a look into the Cat’s Eye as it might appear in dimension. Step inside and let’s learn more…

When Jukka produces an image, it’s more than just a clever Photoshop “trick”. Hours of study must go into each image, because the light is acting differently in each part of the nebula. To make these images work correctly, Jukka must understand which stars are causing the ionization, which stars are nearer and further from our point of perspective and so on. Each type of image is totally unique and what makes dimension work for a reflection nebula won’t work for an emission nebula. Says Jukka; “To be able to make those stereo pairs, one have to learn lots of things about the targets, and beside that, study the actual image more deeply than usual. Star distances must be measured by the size and the color. For example, stars with yellowish hue must be in or behind the nebulosity, white/blue ones are front of it.”

Because dimension will appear reversed by the method you choose to use to view these images, Jukka makes two versions. The first you see at the top of the page is parallel vision – where you relax your eyes and when you are a certain distance from the monitor screen the two images will merge into one to produce a 3D version. The second – which appears below – is crossed vision. This is for those who have better success crossing their eyes to form a third, central image where the dimensional effect occurs. So, now that you understand the images are a visualization and how they are created, let’s take a parallel look…

And now it’s my turn to add a little “magic” to what you see.

Estimated to be 1,000 years old, the Cat’s Eye is a portrait of a dying star – and quite possibly an unresolved double-star system. According to research, the dynamical effects of two stars orbiting one could very well be the cause of the complicated and intricate structures revealed here – structures normally not seen in planetary nebulae. When NGC 6543 was first observed spectroscopically, it showed the presence of emission lines, an indicator of multiple stars, but also an indictor of diffuse gas clouds.

As studies progressed, more hypothesis about the NGC 6543’s structure began to emerge. Perhaps a fast stellar wind from the central star created the elongated shell… It could be the companion star is emitting high-speed jets of gas that lie at right angles to the equatorial ring… Maybe the stellar wind has carved out the inner structure of the nebula are there are more than one there? Says L.F. Miranda; “The velocity field of NGC 6543 shows the existence of two concentric ellipsoidal shells in the nebula. The two shells likely represent the inner and outer surface layers of a geometrically ‘Thick Ellipsoid’ (TE) which constitutes the basic structure of NGC 6543.”

Even more research ensued, and with it came the twin jet theory and the ejection of materials spaced over intervals of time – like cosmic smoke rings being puffed off at perfect intervals. According to Bruce Balik; “Hubble archival images of NGC 6543 reveal a series of at least nine regularly spaced concentric circular rings that surround the famous nebular core, known as the Cat’s Eye Nebula. The rings are almost certainly spherical bubbles of periodic isotropic nuclear mass pulsations that preceded the formation of the core. Their ejection period is consistent with a suggestion that quasi-periodic shells are launched every few hundred years in dust-forming asymptotic giant branch (AGB) winds but not consonant with the predictions of extant models of core thermal pulses (~105 yr) and surface pulsations (~10 yr).”

To be sure, there are simply a lot of things that we don’t know or understand about the Cat’s Eye Nebula just yet. It is possible that magnetic activity somewhat similar to our own Sun’s sunspot cycle, could be at work here. Says Dr. Balick; “What do the rings imply? Since they’re larger than the bright cores of the nebulae that they surround, the rings are almost certainly material ejected episodically before the main and bright core of the nebula formed. This means that the start that ejected the nebulae first quivered and shivered and made these concentric rings. Then something big happened, and the density and mechanism for ejecting the mass changed abruptly. This is when the core of the nebula was formed, typically between 1000 and 2000 years ago. The rhythmic ringing of a dying star is expected as the last of its nuclear fuel is suddenly triggered into ignition by the increasing crush of gravity — much like the juice ejected by squeezing an orange with increasing force. Each expulsion of juice temporarily relieves the internal pressure inside the orange. Similarly, each ejection of mass temporarily stops the combustion of the final dregs of the star’s remaining fuel. Why should the pattern of ejection mass change so radically and strongly? We can only conjecture. Its possible that an orbiting star or giant planet falls onto the dying star. It hits the surface with such force that its atoms ignite in a large conflagration. Somehow, the burst of heat drives the remnants of the dying star into space in fantastic patterns.”

And we looked right into its eye…

My many thanks once again to Jukka Metsavainio of Northern Galactic for his artistry and we look forward to the next installment!