The secret of Saturn’s hexagon

Admittedly, any mystery involving geometry does not sound all that thrilling (though this one does have a sweet video), I promise this one is.

For the last 30 years astronomers have been mesmerized by why Saturn has a gigantic hexagon encircling its North Pole. Most of the distinct bands that characterize Saturn’s surface are circular, formed by gas jet streams at various latitudes. However, when the Voyager spacecraft flew over Saturn in 1988, astronomers noticed that one of the bands is a very distinct hexagon with sides nearly the diameter of earth.

Someone concocted a theory to explain the geometric voodoo and attributed it to a giant vortex along one of the hexagon’s sides. It sounded reasonable; the vortex was certainly big enough to manipulate the course of the planet’s jet stream. But then when Cassini went back a few years ago, the hexagon was still the same as ever and the vortex was nowhere to be seen.

Saturn’s jig is up though.

As explained by Science Now (in much more detail), using a little fluid dynamics some British physicists were able to reproduce the hexagon in their lab. They put a cylinder of water on a spinning table to simulate the planet’s atmosphere and made a mini jet-stream inside the cylinder (the green dye) by placing a small ring in the water that would spin faster than the cylinder itself.

They found that when the ring’s speed increased, the jet stream became less round as eddies were formed on its edges. One of the group members told Science Now that they could create pretty much any shape they wanted including ovals, triangles and squares. The jet stream on Saturn is produced because it spins at a rate that happens to favor a hexagon.

The group also says these forms have been seen in hurricanes for some time and they’re generated pretty commonly in fluid dynamics. It’s just no one bothered to let astronomers in on the secret.

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