30 Years Ago, We Visited Uranus
The crescent of Uranus, imaged by Voyager 2 as it sped away from this distant world.
photo credit: NASA/JPL
 
 
On January 23, 1986, Voyager 2 fly past Uranus, taking pictures and taking many important scientific measurements from just 81,500 kilometers away from the giant greenish-blue ice giant's cloud tops. This flyby gave scientists an treasure trove of incredible observations of the planet, moons, and rings, as well as discovering a large and active magnetic field around the icy world, and even discovering even more rings and moons. These observations are truly one of a kind, as no missions have been to Uranus since this first flyby, and even our modern advanced telescopes can only see limited detail on this distant system. As professional nature photographers can tell you, nothing beats getting up close to really capture the intimate details of a subject, and Voyager was truly an up-close-and personal photographer of our solar system! 
 
0Uranus as spied by Voyager 2
Uranus as spied by Voyager 2 on approach.
Image credit: NASA/JPL

 
 Before Voyager 2 flew past Uranus, scientists only knew a few basic facts about this cold, distant world despite having known of its existence since its discovery by WIlliam Herschel in 1781. Uranus is  2.9 billion miles away from the Sun and the third largest planet in our solar system. Its atmosphere  contains mostly helium and hydrogen with a smattering of methane. Famously, Uranus appeared to be crazily titled to one aide, its poles taking turns facing our Sun during its 84 Earth-year orbit around the Sun. A few moons had been observed. Its rings had only recently been discovered by the Perth Observatory in Australia and airborne Kuiper observatory (a precursor to SOFIA) during an occultation of a star by Uranus in 1977. 
 
Scientists added a rich new amount of data to their knowledge of Uranus during and after Voyager 2 sped past the system. Its dark ring system was observed in great detail, and two new rings were discovered. In addition to the rings, 10 new Moons were also discovered. Most surprising was the discovered of a magnetic field, a very large one that defied normal expectations. 

Image of fine detail in the rings of Uranus

Close up, high-angle view of fine detail in the rings of Uranus by Voyager 2. The streaks in this image are stars in the background, as the cameras on Voyager 2 were trained on the rings as it quickly sped by.
Image Credit: NASA/JPL/NASA Photojournal
 
The atmosphere, in contrast to this list of happy surprises, seemed to be a bit of a disappointment at first: the first imaged revealed bland, nearly featureless cloud tops, tinged greenish-blue from methane. Oddly enough, the temperatures at the sun-facing pole of the planet were found to be almost the same as the temperature at the equator, leading scientists to speculate that this odd uniformity of temperature around the planet was what caused the clouds to seem so featureless and storm-free. Appearances can be deceptive, however:more recent observations by powerful infrared and optical telescopes on Earth have revealed powerful storms sweeping through the planet's cloudtops. So  perhaps Voyager 2 simply visited an a quiet time in the planet's normal weather cycle. 

Can you see Uranus at night? From a very dark and clear sky, you may be able to make out this planet with your own two eyes; if you can see Uranus at all, it will appear like a faint star. It is much easier to spot using binoculars, and with a telescope you can begin to make out its round shape and greenish-blue color. With a very large telescope and some creative use of filters, you may even just be able to make out a storm on its cloud tops, if you are very lucky, or even spot a moon or two. Check out this guide from Sky & Telescope on how to spot both Uranus and Neptune from your backyard or favorite observing site. 

NASA has more information and pictures on Uranus on their Solar System Exploration site. There have been a few proposals to revisit the Uranus system, and visiting this icy giant has been identified as a scientific priority; perhaps thirty years from now we will have all-new sets of images and date from the edge of our solar system that may revolutionize our understanding of Uranus once again!


Image of Uranus taken byt he Keck Observatory
Image of Uranus taken by the Keck Telescope, showing the amazing images resulting from modern adaptive optics. You can see structure in the rings and in the cloud system, including white storms. Advances such as these in our modern powerful telescopes have allowed us to continue to study Uranus and other distant solar system objects in some detail and make even more valuae discoveries about this complex world.

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Image Credit:Heidi Hammel, Space Science Institute, Boulder, CO/Imke de Pater, University of California, Berkeley/ W. M. Keck Observatory 


 
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