Uranus

Article By:

Lissauer, Jack J. Space Science and Astrobiology Division, Planetary Systems Branch, Ames Research Center, National Aeronautics and Space Administration, Moffett Field, California.

Marley, Mark S. Space Science and Astrobiology Division, Planetary Systems Branch, Ames Research Center, National Aeronautics and Space Administration, Moffett Field, California.

Last reviewed:March 2019

DOI:https://doi.org/10.1036/1097-8542.722800

Show previous versions

• Uranus, published January 2014:Download PDF Get Adobe Acrobat Reader

The first planet to be discovered with the telescope and the seventh in order of distance from the Sun. Uranus is the farthest planet from Earth that can be spotted with the naked eye. Along with Neptune, it is one of two "ice giants" in our solar system. Ice giants are large worlds composed mostly of elements heavier than hydrogen and helium, in distinction to gas giants, such as Jupiter and Saturn, whose compositions are dominated by this pair of light elements. Only a single spacecraft, Voyager 2, has visited Uranus. The space probe flew by in early 1986, making its closest pass on January 24, coming within a distance of 81,500 km (50,600 mi) to the world's cloudtops. Voyager 2 obtained the most detailed images of the planet to date (Fig. 1). Remarkable features of Uranus include the lack of an internal heat source, a system of thin rings, and high obliquity, or axial tilt, with the planet spinning on its axis perpendicularly to its orbital path. See Table 1 for planetary and orbital characteristics of Uranus. See also: Astronomy; Earth; Eye (vertebrate); Jupiter; Neptune; Planet; Saturn; Space probe; Solar system

The content above is only an excerpt.