48 Fun Facts About Uranus

Where does Uranus rank in distance from the Sun?

Seventh. It orbits about twice as far out as the sixth planet, so its discovery in 1781 roughly doubled the width of the known Solar System.

Uranus was the first planet to be discovered with the help of what?

A telescope. The astronomer who found it built his own, and in 1781 it showed him a faint object creeping against the background stars from night to night.

What did Herschel first report his new object to be?

A comet. He kept calling it one for months, but its nearly circular path convinced other astronomers it was a planet, and by 1783 he agreed.

What name did Herschel want to give Uranus, in honour of his royal patron?

Georgium Sidus, or George's Star. Herschel reasoned the name would tell future ages that the planet first came to light in the reign of George III.

In myth Jupiter was Saturn's son, so Bode named the next planet after Saturn's what?

Father. Bode wanted the new planet to extend the mythological family line outward from Jupiter, and by about 1850 his name had displaced every rival.

Uranus is the only planet whose English name comes from which mythology?

Greek. The name was chosen to match the other planets, yet theirs are all Roman; the matching pick would have been Caelus, the Roman counterpart of Ouranos.

In ancient myth, Uranus (Ouranos) was the god of what?

The sky. Ouranos was the heavens personified and husband of Gaia, the Earth; in Hesiod's poem their youngest Titan son ambushed and overthrew him.

A spacecraft trying to land on Uranus would do what?

Sink until it was crushed. Uranus has no solid surface to land on: its gases simply thicken with depth, and the rising pressure and temperature would destroy a metal craft long before it reached anything firm.

In which country did the name Herschel chose for Uranus stay in use for decades?

Britain. Astronomers elsewhere refused to honour a foreign king, and Uranus only became the standard name around 1850, almost 70 years after the discovery.

Uranus's rotation axis is tilted so far that the planet essentially does what?

Rolls on its side. With the axis tipped about 98 degrees, one pole points almost straight at the Sun for part of each orbit while the other faces away into night.

How long is a year on Uranus?

84 Earth years. A single lap lasts about a human lifetime: Uranus first returned to the spot where it was discovered in 1865, and only for the second time in 1949.

Because Uranus orbits tipped over, it has the Solar System's most extreme what?

Seasons. Each lasts about 21 Earth years, and around midsummer one pole faces the Sun almost directly while the other half of the planet sits through a long, sunless winter.

Uranus spins in the opposite direction to most planets, a quirk it shares with which other planet?

Venus. Both turn the opposite way to the other six planets, so on Venus the Sun rises in the west; one backward spin of Uranus takes about 17 hours.

Unlike the larger gas giants, Uranus and its outer neighbour are classed as what type of planet?

Ice giants. The name misleads: most of the planet is a hot, dense fluid of water, ammonia and other 'icy' compounds that reaches thousands of degrees near the core.

Uranus holds which Solar System record?

Coldest atmosphere. It has dipped to 49 K, about −224 °C, colder than anything measured on Neptune, which orbits a billion miles farther from the Sun.

Compared with the other giant planets, Uranus gives off surprisingly little of what?

Internal heat. The other giant planets all give off markedly more energy than the Sun supplies them, while Uranus radiates scarcely any extra, and no one is sure why.

What is the leading explanation for Uranus's tilt?

An Earth-sized impact early in its history. The blow is thought to have knocked the young planet over, and its rings and moons now circle it sideways too.

Only two planets are wider than Uranus, but where does it rank among the planets by mass?

Fourth. Neptune is slightly smaller across but denser, so it outweighs Uranus, which at about 14.5 Earth masses is the lightest of the four giant planets.

What do scientists think may rain down deep inside Uranus?

Diamond 'hailstones'. In 2017 physicists shocked plastic with a powerful laser to mimic those depths and watched tiny diamonds form; inside the planet they would slowly settle toward the core.

Which telescope's 2023 infrared image showed 11 of Uranus's 13 rings?

Webb. A 12-minute exposure was enough to pick out dusty rings that only a passing spacecraft and the Keck Observatory had managed to image before.

How were Uranus's rings discovered in 1977?

A star flickered as they crossed it. Astronomers on a flying observatory only meant to watch Uranus hide the star, but it blinked out five times before the planet arrived and five times after.

The main rings of Uranus are notably what?

Dark. They bounce back only about 2% of the sunlight that hits them, and are thought to be ice coated in material that radiation has blackened.

The moons of Uranus are named after characters from which two writers?

Shakespeare and Alexander Pope. Moons elsewhere are mostly named for figures from classical myth; these alone take theirs from English literature.

Astronomers found in 2018 that the clouds of Uranus hold a gas that would make them smell of what?

Rotten eggs. The culprit is hydrogen sulfide, which the Gemini North observatory in Hawaii picked out above the cloud tops after decades of hints from deeper down.

What is the largest moon of Uranus?

Titania. Even the biggest of the family is less than half as wide as our Moon, about 1,600 km across, and it is scarred by fault valleys almost as long as the moon is wide.

Which small moon of Uranus has fault canyons 20 km deep and a chaotic patchwork surface?

Miranda. Its gravity is so feeble and its cliffs so tall that a rock dropped from the highest, Verona Rupes, would fall for around ten minutes before landing.

The last of Uranus's five large moons was found in 1948 by which astronomer?

Gerard Kuiper. He spotted the little moon in photographs taken at McDonald Observatory in Texas, and no further moon turned up until a spacecraft arrived almost four decades later.

Which is the only spacecraft to have visited Uranus?

Voyager 2. Originally meant to visit just two planets, it rode a planetary line-up that comes round once every 175 years and flew on to Uranus.

Which space disaster struck just four days after the only spacecraft flyby of Uranus?

Challenger. The shuttle was lost on 28 January 1986, four days after the closest approach, so the first close-up pictures of Uranus shared the week's news with a tragedy.

What did the only spacecraft to visit Uranus find odd about its magnetic field?

It is tilted and off-centre. The magnetic axis leans 59 degrees from the spin axis and misses the planet's centre by a third of its radius, so the auroras sit far from the poles.

What did the only close-up pictures of Uranus show?

A nearly featureless ball. The passing probe picked out only about ten clouds on a bland globe, yet later views have caught bright storms and winds of up to 900 km/h.

Astronomers had recorded Uranus many times before 1781, each time mistaking it for what?

A faint star. John Flamsteed entered it in his star catalogue in 1690, and its dimness and sluggish pace kept anyone from noticing that it moved.

Irregularities in Uranus's orbit led to the prediction and discovery of which planet in 1846?

Neptune. A French mathematician worked out where an unseen world must be tugging on Uranus, and a Berlin astronomer found it on his first night of searching.

Which pronunciation of Uranus do astronomers prefer?

YOOR-ə-nəs, stress on the first syllable. It follows the Latin stress, and it spares scientists the schoolyard joke that the more common second-syllable version invites.

Uranus's name translates as what in Chinese, Japanese, Korean and Vietnamese?

Heavenly King star. East Asian astronomers translated the meaning of the Western names rather than the sound, so the next planet found became the Sea King star.

What was William Herschel's profession when he discovered Uranus in 1781?

Musician. Herschel earned his living as an organist and composer and took up astronomy as a hobby; finding a planet let him give up the day job for good.

Which sign of the zodiac has Uranus as its ruling planet in modern astrology?

Aquarius. The sign already had a traditional ruler, but modern astrologers gave it the planet found in 1781 as well, casting the newcomer as the bringer of rebellion and sudden change.

Which composer's orchestral suite includes a movement for Uranus?

Gustav Holst. His suite The Planets paints each world's astrological character rather than its astronomy, which is why Uranus appears as 'the Magician'.

Which poet compared a great discovery to the moment 'a new planet swims into his ken'?

John Keats. In his 1816 sonnet on Chapman's Homer he feels like a watcher of the skies, an image usually read as Herschel finding Uranus.

What gives Uranus its cyan colour?

Methane in its atmosphere. The gas soaks up the red part of sunlight, so the light that bounces back off the cloud tops comes out blue-green.

The Uranus mission that US scientists ranked their top priority in 2022 would be the first to do what?

Orbit the planet. The proposed craft would circle Uranus for years and drop a probe into its clouds; every close-up so far comes from one brief flyby in 1986.

A 2023 NASA study suggests four of Uranus's largest moons may hide what beneath their crusts?

Oceans of liquid water. Most of these moons were thought too small to avoid freezing solid, but the modelling found enough warmth inside to keep a buried layer, perhaps dozens of miles deep, liquid.

Uranus is the second least dense planet, after which?

Saturn. It is the only planet whose average density is lower than water's, so in a big enough bathtub it would float, which not even Uranus could manage.

Uranus's rings are thought to be young and to be the remains of what?

A shattered moon or moons. The rings look no more than about 600 million years old, far younger than Uranus itself, so they are read as rubble from moons that broke apart.

From the garden of his house in which English city did Herschel first observe Uranus on 13 March 1781?

Bath. His house at 19 New King Street is now the Herschel Museum of Astronomy, and the instrument he used that night was one he had built himself.

Herschel found Uranus from England, but in which present-day country was he born?

Germany. He was born Friedrich Wilhelm Herschel in Hanover, crossed to England at 19 to find work, and turned himself into plain William.

How did the king reward Herschel for finding Uranus?

A salaried court post. As the king's own astronomer he moved to a village near Windsor Castle, where he was expected to show the royal family the heavens on request.

Which relative worked as William Herschel's assistant and became the first woman to earn a salary as an astronomer?

His sister. Caroline Herschel ground mirrors and worked through his calculations, then made discoveries of her own, and in 1787 the king put her on the payroll.