📖 About Uranus

Uranus is the seventh planet from the Sun and the third-largest in our solar system, with a diameter of 51,118 km. Classified as an “ice giant” along with Neptune, Uranus is composed primarily of water, methane, and ammonia ices surrounding a small rocky core. Its pale blue-green color comes from methane in the atmosphere, which absorbs red light and reflects blue.

Uranus’s most distinctive feature is its extreme axial tilt of 98 degrees—it essentially rolls around the Sun on its side. This means each pole gets about 42 years of continuous sunlight followed by 42 years of darkness. Scientists believe a massive collision with an Earth-sized body early in the solar system’s history knocked Uranus onto its side. Deep in the atmosphere, extreme pressures may compress methane into diamonds that rain toward the core.

The 2023 Planetary Science and Astrobiology Decadal Survey selected a Uranus Orbiter and Probe (UOP) as its top-priority flagship mission. This would be only the second spacecraft to visit Uranus—Voyager 2 flew past in January 1986, our sole encounter. The proposed mission would study Uranus’s atmosphere, interior, magnetosphere, rings, and moons during a multi-year orbital tour, revolutionizing our understanding of ice giant planets.

🔭 Key Features

🔬 Science & Future

Uranus and Neptune represent a class of planet—ice giants—that is the most common type in the galaxy, yet the least studied in our solar system. Understanding Uranus is crucial for interpreting the thousands of similar-sized exoplanets discovered by Kepler and TESS. The planet’s unusual magnetic field, tilted 59 degrees from its rotation axis, adds to the mystery.

The Uranus Orbiter and Probe mission would launch in the early 2030s and arrive in the 2040s, studying the planet for several years. Key questions include: What is inside Uranus? Why is its magnetic field so tilted and off-center? How do its rings and moons interact? What caused its extreme tilt? These answers will transform our understanding of planetary formation throughout the cosmos.

📜 Discovery & Exploration

William Herschel discovered Uranus on March 13, 1781—the first planet found with a telescope. Initially he thought it was a comet, but its nearly circular orbit confirmed it as a planet. The name Uranus, after the Greek god of the sky, was proposed by Johann Bode and gradually adopted over several decades.

Voyager 2’s January 1986 flyby remains humanity’s only visit to Uranus. The spacecraft discovered 10 new moons, two new rings, and measured the planet’s peculiar magnetic field. Images of Miranda’s dramatic cliff faces and chaotic terrain were among the most surprising. After nearly four decades, the planetary science community has made returning to Uranus its highest priority.