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Discovered by Sir William Herschel in 1781, the seventh planet in our solar system is named for the Greek deity Uranus, the original skygod of the Greek cosmology.  In classical myth Uranus was castrated and supplanted by his youngest son Cronus (Saturn) who then fell before Zeus (Jupiter) and indeed, the third largest planet in our solar system (in volume) is often overlooked by astronomers, whose eyes are trained on the dramatic gas-giants Jupiter and Saturn.  Only one mission has flown by Uranus–Voyager II, which captured the following undramatic photo in 1986 as it whipped through on its way to Neptune.

Photograph of Uranus taken by Voyage II in 1986 (not a cue ball!)

All of this is a shame, Uranus is not only the first ice-giant planet but it is unique in the solar system for rotating vertically rather than horizontally (probably thanks to some apocalyptic super collision long ago in the planet’s history). From our perspective, the moons of Uranus orbit around it like a clock’s hands and its sporty red rings sometimes give it the appearance of a target.  Uranus has an incredibly long rotation around the sun.  One Uranus year equals 84 Earth years.  Because it spins vertically rather than horizontally, one pole is cast in a super winter which lasts twenty of our earth years (remember the poles of Uranus are on the equator).  Voyager flew by during the deep freeze of winter to get that boring photo up there, but now the seasons are changing and spring is coming to Uranus’ northern pole while fall is coming to the south (I wish there were a different name for the side poles—this is really confusing to write about).

Planet Uranus is seen in this composite image by the Keck II Telescope at near-infrared wavelengths. (Lawrence Sromovsky, UW-Madison Space Science and Engineering Center)

Because of the seasonal change, huge storms (the size of a continent on Earth) are tearing through the Uranian atmosphere with 500 kilometer-per-hour methane winds.  Keep in mind that Uranus has the coldest atmosphere in the solar system, probably because the collision which knocked it on its side dissipated its primordial heat (although nobody really knows). Temperatures there get down to a chilly –224 °C.  Brrr!

A similar bright spot photographed by Hubbel in 2005 just before the vernal equinox

The spring storms are apparently dramatic and fierce enough to be seen from Earth.  Yesterday astronomers reported the appearance of a huge white speck with an albedo ten times that of the planet.  This methane storm probably looks like an immense immense thundercloud spreading above the usually placid blue cloud cover of the ice world.  Saturn has been going through its own cycle of super storms recently (in addition to the great hexagonal storm raging on its north pole).  Its tempting to adapt the folksy mannerisms of country smalltalk and suggest that weather in the solar system has been bad lately–but humankind is probably only just now able to apprehend such phenomena!

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