Saturn’s Hexagon

Saturn's hexagon

Saturn’s hexagon is a persisting hexagonal cloud pattern around the north pole of Saturn. The sides of the hexagon are about 9,000 miles long, which is more than the diameter of Earth. The hexagon is about 18,000 miles wide, may be 190 miles high, and may be a jet stream made of atmospheric gases moving at 200 mph.

It rotates with a period of 10h 39m 24s, the same period as Saturn’s radio emissions from its interior. The hexagon does not shift in longitude like other clouds in the visible atmosphere.

Saturn’s hexagon was discovered during the Voyager mission in 1981 and was later revisited by Cassini-Huygens in 2006. Between 2012 and 2016, during the Cassini mission, the hexagon changed from a mostly blue color to more of a golden color. The color change is potentially due to seasonal changes exposing the pole to sunlight, creating a haze. Saturn’s south pole does not have a hexagon, as verified by Hubble observations; however, it does have a vortex, and there is also a vortex inside the northern hexagon.

Cassini was able to take only thermal infrared images of the hexagon until it passed into sunlight in 2009. Cassini was also able to take a video of the hexagonal weather pattern while traveling at the same speed as the planet, therefore recording only the movement of the hexagon. After its discovery, and after it came back into the sunlight, amateur astronomers managed to get images showing the hexagon from Earth.

Between 2012 and 2016, the hexagon changed from a mostly blue color to more of a golden color. One theory for this is that sunlight is creating haze as the pole is exposed to sunlight due to the change in season. These changes were observed by the Cassini spacecraft.

One hypothesis for the hexagon, developed at Oxford University, is that it occurs where there is a steep latitudinal gradient in the speed of the atmospheric winds. Similar regular shapes were created in the laboratory when a circular tank of liquid was rotated at different speeds at its center and periphery. The most common shape was six sided, but shapes with three to eight sides were also produced. The shapes form in an area of turbulent flow between the two different rotating fluid bodies with dissimilar speeds.

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