In fact, Uranus has been breaking the mold as long as we’ve known about
it. Mercury, Venus, Mars, Jupiter, and Saturn are all easily visible to
the naked eye; humans have been gazing at those planets for millennia,
but Uranus was the first planet discovered by modern astronomy. It’s so
far away, and its movement so slow, that it was originally thought to be
a star until Sir William Herschel revealed its planetary nature in
1781. Less than a decade later, it received a namesake chemical element:
uranium, discovered in 1789. (Meanwhile, Neptune and Pluto didn’t make
it into the periodic table for another 150 years.)
The more astronomers studied this new planet, the clearer it became that
it was an odd one. Consider the seasons on a world turned sideways:
Summer on Uranus is two decades of non-stop sunlight, and winter is an
equal amount of time spent in total darkness, facing the cold void of
distant space. Day and night only exist during spring and fall, where
they cycle every 17 hours. Some have suggested that the planet was
knocked askew by a gravitational tug-of-war with a large moon that has
since been lost; others have proposed that it was the result of a
collision with a massive object (much larger than Earth), or even
multiple collisions.[...]
Perhaps Uranus wouldn’t be quite so mysterious if more spacecraft
stopped by—but while Mars, Jupiter, and Saturn seem to receive a
constant stream of high-tech fan-mail from Earth, Uranus has only been
visited once. In 1986, Voyager 2 swung by on its way into deep space. It
was the first and so far the only mission to get an up-close view of
Uranus, and what the probe saw was, at first glance, dull. Voyager 2
observed little atmospheric activity, and few cloud formations. For a
moment, it seemed the icy clouds held little of interest. But it’s been
30 years since the Voyager fly-by, and we’re wiser now.
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