Planet
Uranus
The sideways planet, rolling around the Sun on its side.
Uranus is tipped 97.77 degrees, so it rolls along its 84-year orbit almost on its side. For about a quarter of each orbit, one pole faces the Sun while the other endures a 21-year night. It also spins backward relative to most planets.
How it moves
- Uranus orbits the Sun every 30,685 days (about 84 Earth years) at an average of 6.79 km/s.
- Its axis is tilted 97.77 degrees, so the planet effectively spins on its side.
- It rotates retrograde once every 17.24 hours.
- For nearly a quarter of each Uranian year the Sun shines almost straight down on one pole, leaving the other in a 21-year winter night.
- Earth laps Uranus every 369.66 days (synodic period), producing a small retrograde loop each year.
Facts
- Mean radius
- 25,362 km
- Mass
- 8.681e+25 kg
- Surface gravity
- 9.01 m/s²
- Rotation period
- 17.24 hours
- Orbital period
- 30,685.4 days
- Average distance from the Sun
- 19.19126393 AU
- Eccentricity
- 0.0469
- Axial tilt
- 97.77°
- Mean orbital speed
- 6.79 km/s
- Known moons
- 29
- Discovered
- March 13, 1781, by William Herschel (first planet found with a telescope)
Each pole of Uranus gets about 21 years of continuous darkness during its winter.
Sources: nssdc.gsfc.nasa.gov, science.nasa.gov, science.nasa.gov