Uranus is the seventh planet from the Sun and is the third largest in the solar system. It was discovered by William Herschel in 1781 with a telescope as opposed to the naked eye. It is at times possible to view Uranus with the naked eye but it is difficult to see because of its similarity to stars in the background. Most of what we know about Uranus came from Voyager 2’s flyby in 1986. The spacecraft discovered 10 additional moons and several rings before heading on to Neptune.
We now know that Uranus has 27 moons. Five of its largest moons are named Miranda, Titania, Oberon, Umbriel and Ariel. Many of the moons of Uranus are named for characters in the works of William Shakespeare and Alexander Pope. The two largest moons, Titania and Oberon, were discovered by William Herschel in 1787. The very largest is Titania but it is still only half the size of the Earth’s moon.
We can now count nine rings around Uranus. These rings are distinctly different from those around Jupiter, Saturn and Neptune. The outermost epsilon ring is composed mostly of ice boulders several feet across.
Uranus is a gas giant, as are Jupiter, Saturn and Neptune. A gas giant is not primarily composed of rock or other solid matter on its surface. Uranus has a small core containing silicates but most of its gas consists of water, methane and ammonia. Its atmosphere is 83% hydrogen, 15% helium, and 2% methane. The methane gives Uranus a blue-green color.
Uranus is named after the Greek god of the sky. Its diameter is 32,190 miles as compared with the diameter of the Earth which is approximately 7,926 miles. Because of its large size, it takes 84 years for Uranus to complete its orbit around the sun as compared to Earth which takes 365 days to orbit the sun. The period of rotation on Uranus is 17.24 hours; the rotation of Earth is completed in 24 hours. It is interesting that Uranus’ rotation is retrograde; that is, it spins backwards compared to most other planets. The temperature of Uranus is -322.87 degrees Fahrenheit, which of course makes it inhabitable by humans from Earth.
Uranus is also distinguished by the fact that it is tipped on its side at an axis of 98 degrees. The severe tilt is thought to have resulted from a huge collision with a planet-sized body early n the solar system’s history.
Planetary scientists recently reported a new study that there are planets outside of our solar system measuring 5 to 30 times the size of Earth. They also suggest that solar systems with Earth-size planets may be common. New technology allows these scientists to compile data that had previously been unavailable.