What Is Uranus?
Uranus is the seventh planet from the Sun, located between Saturn and Neptune, the sixth and eighth planets from the Sun, respectively. The planet is the third largest in the Solar System in terms of radius, and the fourth largest in terms of planetary mass. Therefore, along with Jupiter, Saturn, and Neptune, Uranus is one of the four "giant planets" in the Solar System. Given their similar composition, Uranus and Neptune are both described as "ice giants," while Jupiter and Saturn are considered "gas giants." Uranus has the lowest temperature of any planet in the Solar System, which can reach as low as −371 °F. The interior of the planet is mainly composed of rocks and ice, and it has a ring system, like the other giant planets, a number of moons, and a magnetosphere. Uranus is visible from Earth with the naked eye, although its slow orbit and dimness delayed its identification as a planet by ancient observers. German-British astrologist Sir William Herschel officially discovered the planet on March 1, 1781, after the invention of the telescope. The discovery of the planet signaled the very first time the Solar System was expanded.
Prior to the discovery of telescopes, the ancient Romans could only see seven bodies in space. These bodies were bright and included five bright planets, as well as the Sun and Moon. Ancient Roman astronomers named visible planets after Roman gods, and after the invention of telescopes, astronomers continued this tradition and drew upon the names of Roman gods for new planets. However, an exception was made for Uranus, since the name is the only one that is based purely on Greek mythology. The name "Uranus" is a reference to the Greek god of the sky, Uranus. According to Greek mythology, Uranus was the grandfather of Zeus (Jupiter) and father of Cronus (Saturn).
Upon discovery of the planet, Herschel wanted to name it Georgium Sidus, in honor of King George III, who was his patron. Essentially, the name meant the "Georgian Planet" or "George’s Star." However, the name was not a popular choice outside of Britain, and so alternative names were proposed. For example, French astronomer Jérôme Lalande proposed the name "Herschel" in order to honor the person responsible for its discovery, while the name "Neptune" was proposed by Swedish astronomer Erik Prosperin. Some British astronomers liked Prosperin's proposed name, yet with a slight modification to either Neptune Great Britain or Neptune George III in honor of the British Royal Navy. Eventually, the astronomers settled on the name Uranus in March 1782, upon the recommendation of German astronomer Johann Elert Bode.
Name in Other Languages
In other languages, the planet is known by a number of other names. For example, China, Vietnam, Korea, and Japan refer to the planet as the "Sky King Star." Mongolians call it "King of the Sky," while Hawaiians call it "Hele‘ekala," which is a name based on its discoverer.