Above: Uranus captured by Voyager 2 in January 1986 (Credit: NASA/JPL).
Quick Fact File
51,117 km – the diameter (31,763 miles) of the planet.
25,362 km – the equatorial radius (15,759 miles).
400% – comparison in size to Earth.
159,354 km – the equatorial circumference (99,018 miles).
8,083,079,690 km² – the surface area (3,120,894,516 mi²).
3.00 billion km – maximum distance from the Sun (1.86 billion miles).
2.75 billion km – minimum distance from the Sun (1.71 billion miles).
2.88 billion km – average distance from the Sun (1.79 billion miles).
2.57 billion km – closest distance to Earth (1.6 billion miles).
84 years – the orbital period of the planet Uranus – the time taken to orbit the Sun in Earth years (84.011 years).
30,687 days – the time taken to orbit the Sun in Earth days (30,687.15 days).
17 hours – the rotation period – the time taken for the planet to rotate on its own axis (17.24 hours).
0.25% – the equivalent amount of the sunlight that reaches Earth that reaches Uranus.
24,515 km/h – the speed that Uranus travels through space, relative to the sun (15,233 mph); it is the second slowest of the planets, only the planet Neptune is slower.
6.81 km/s – that speed expressed in terms of distance covered each second (4.23 mi/s).
30,687 days – the length of a year on Uranus, in Earth days (30,687.15 days).
13 March 1781 – the date Uranus was discovered by William Herschel (1738 – 1822), an amateur astronomer, who thought it to be “a curious nebulous star or perhaps a comet”.
1986 – the year that Voyager 2 passed Uranus, sending back images that revealed a fairly featureless planet.
42 years – the length of time that a single night or day lasts at the North and South poles of Uranus.
500 kph – the approximate maximum speed (300 mph) that winds can reach around the planet.
5,000°C – the estimated minimum temperature (9,000°F) of the core of Uranus.
10 million – the amount by which you would need to multiply the atmospheric pressure on Earth’s surface in order to match the pressure on the core of Uranus.
15,000 km – the estimated depth (9,300 mi) of the mantle of Uranus.
Did You Know?
The mantle of Uranus is made up of water, ammonia and methane. Ordinarily, at this distance from the sun, these would freeze. However, the heat generated by the planet’s molten core means the mantle is instead a dense ocean.
-224°C – the temperature (-371° Fahrenheit) to which the troposphere (the dense region of the planet’s atmosphere) can plunge. Although Uranus is not the farthest planet from the sun (Neptune is) it is the coldest planet in our solar system.
13 – the number of rings circulating Uranus, comprised mainly of dust and rock, and very dark in colour.
1977 – the year in which rings were first detected, when they were found to be blocking light from a star. More rings were discovered in 1986 (by Voyager 2) and in 2003-05 (by the Hubble space telescope).
Moons of Uranus
27 – the number of moons orbiting Uranus.
3 – the number of groups into which these moons are classified (there are 5 major moons, 13 small inner moons, and 9 small outer moons).
1787 – the year William Herschel (1738 – 1822) discovered the two largest moons, Titania and Oberon, six years after discovering Uranus itself.
1851 – the year amateur astronomer William Lassell (1799 – 1880) identified the next two biggest moons, Umbriel and Ariel.
1948 – the year Gerard Kuiper (1905 – 1973) discovered the fifth major moon, Miranda.
Above: Miranda, the fifth largest and innermost moon orbiting Uranus, captured by Voyager 2 in January 1986. Area shown is around 250 km (150 mi) wide, and captured from a distance of 36,000 km (22,000 mi) (Credit: NASA/JPL).
Did You Know?
Uranus’s two largest moons, Titania and Oberon, are amongst the 10 largest moons in our solar system. Yet, such are the differences in scale amongst our planets that all 23 of Uranus’s moons combined would still have less mass than either of the largest moons orbiting Jupiter (Ganymede), Saturn (Titan) and Neptune (Triton).