Uranus
Properties
Position & Identifiers
Physical Properties
Orbital Properties
Observing Tips
Discovery
Current Ephemeris
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About Uranus
Description
Uranus is the seventh planet from the Sun, orbiting at 19.2 AU. It is an ice giant with a diameter of 51,118 km (four times Earth's), composed primarily of water, methane, and ammonia ices surrounding a small rocky core. Methane in the upper atmosphere absorbs red light, giving Uranus its distinctive pale blue-green color. The planet's most remarkable feature is its extreme axial tilt of 97.8 degrees — it essentially rolls around the Sun on its side, likely the result of a massive collision early in its history. This means its poles take turns pointing almost directly at the Sun during its 84-year orbit. Uranus has 28 known moons and a faint ring system discovered in 1977.
Observing Tips
At magnitude 5.7, Uranus is technically visible to the naked eye under perfect conditions, but you need a chart to distinguish it from a faint star. Binoculars make it easy to find once you know where to look — it appears as a star-like point with a slight blue-green tint. A telescope at 100-200x reveals a tiny disk of about 3.5-4 arcseconds, distinctly non-stellar and with a subtle blue-green hue that confirms the identification. Surface detail is essentially invisible from Earth even in the largest amateur telescopes. The five brightest moons (Titania, Oberon, Ariel, Umbriel, and Miranda) require at least an 8-10 inch telescope to glimpse. Uranus moves slowly through the zodiac, spending about 7 years in each constellation.
History
Uranus was the first planet discovered using a telescope. William Herschel found it on March 13, 1781, during a systematic survey of the sky from his garden in Bath, England. He initially thought it was a comet. The planet was eventually named after the ancient Greek god of the sky. Its ring system was discovered in 1977 during a stellar occultation observed from an airborne telescope. Voyager 2 is the only spacecraft to have visited Uranus, flying past in January 1986 and revealing its moons, rings, and extreme axial tilt in detail. A dedicated Uranus orbiter mission has been recommended as a top priority for future exploration.
Fun Facts
Because of its extreme tilt, a single 'day' at Uranus's poles lasts 42 Earth years of continuous sunlight followed by 42 years of darkness. Uranus is the coldest planet in the solar system, with atmospheric temperatures dropping to -224°C — even colder than more distant Neptune — possibly because it radiates almost no internal heat. All 28 of its moons are named after characters from the works of William Shakespeare and Alexander Pope.
Community Photos (1)
Credit: Ardenau4. License: CC0. (Wikimedia Commons)
Skybred Feb 28, 2026