Located in the outer fringes of the Solar System, the ice giant Uranus (pronounced “YOU-ruh-nuss”) never ceases to captivate with its myriad moons, ring system, peculiar tilt, and the composition of its aqua atmosphere. Read on to discover some interesting Uranus facts.
Facts about Uranus
1. Uranus is the seventh planet from the Sun.
Uranus is the seventh planet from the Sun – only Neptune lies further. On average, Uranus is 2.87 billion km (1.78 billion miles) from the Sun.
At its closest (perihelion), Uranus is 2.73 billion km (1.70 billion miles) from the Sun. At its furthest (aphelion), Uranus is just over 3 billion km (1.86 billion miles) from the Sun.
2. Uranus is is the third-largest planet with respect to diameter and is the fourth-largest in terms of mass.
With a diameter of 50,724 km (31,518 miles), Uranus is the third-largest planet in the Solar System behind Jupiter and Saturn. Compared to Earth, Uranus is about four times wider.
With a mass of 8.68 x 1025 kg, Uranus is the fourth-heaviest planet in the Solar System behind Jupiter, Saturn, and Neptune. Uranus has 14.5 times as much mass compared to the Earth.
3. You could fit 63 Earths inside Uranus and still have room to spare.
The volume of Uranus is 6.83 x 1013 km3. To be precise, you could fit 63.08 Earths inside Uranus!
4. Uranus is the second least dense planet in the Solar System, after Saturn.
With a mean density of 1,270 kg/m3, Uranus is the Solar System’s second least dense planet. Earth, which is the densest planet in the Solar System, is 4.3 times denser than Uranus.
5. Uranus Receives 1/400th the energy that Earth receives from the Sun.
Given that Uranus is so far away from the Sun, it receives 0.25% of the amount of sunlight that reaches Earth from the Sun. It takes 2 hours 39 minutes and 42 seconds for the Sun’s light to reach Uranus.
In comparison, it takes 499 seconds (8 minutes and 19 seconds) for the Sun’s light to reach Earth.
6. Like Venus, Uranus spins clockwise.
Uranus, like Venus, spins in retrograde rotation (east-to-west). All other planets in the Solar System spin in a counter-clockwise fashion, while Venus and Uranus spin clockwise (as viewed from above the North Pole).
7. Uranus was the first planet discovered with a telescope.
One of the interesting Uranus facts is that it is the most distant planet from the Sun visible to the naked eye (albeit extremely rarely). It had been observed on numerous occasions before its recognition as a planet, but it was mistaken for a star.
On 13 March 1781, German-born British astronomer William Herschel discovered Uranus using a state-of-the-art 2.1-m-long (7-ft) reflecting telescope. Uranus was finally accepted as a planet of the Solar System in 1783.
Uranus’s recognition as a planet in 1783 made it the first planet to be discovered (recognized) with a telescope. Galileo had spotted Neptune through a telescope as early as 1612 but thought it to be a star. Neptune was only “officially discovered” in 1846.
Bizarrely, Uranus was recognized as a planet before the discovery of Antarctica, whose first confirmed sighting occurred in 1820.
8. Uranus was originally going to be called “George’s Star” (Georgium Sidus).
William Herschel originally tried to name his discovery “George’s Star” (Georgium Sidus), after British King George III. Unsurprisingly, it was an unpopular choice and no one outside Britain agreed to this name.
9. Besides Earth, Uranus is the only planet whose name is derived from a figure from Greek mythology rather than Roman mythology.
Uranus’s name was proposed by German astronomer Johann Bode. Uranus is the Latinized name of the Greek god of the Sky “Ouranos.” His Roman name is Caelus.
10. Uranus has a shorter day than we have here on Earth.
On its axis, Uranus rotates at a speed of 2.59 km/s which is much faster than the speed at which the Earth rotates (0.46 km/s). In contrast to Earth’s 24-hour day, Uranus’s day is 17 hours, 14 minutes, and 24 seconds, almost one-third shorter than our rotational cycle.
11. Uranus orbits the sun every 84 Earth years.
While Uranus rotates faster than Earth on its axis, its orbital velocity is much slower. In fact, Uranus has the second-slowest orbital velocity (6.8 km/s) of all the planets in the Solar System.
Its sluggishness means it takes Uranus a whopping 84.01 Earth years, or 30,685 Earth days, to make one trip around the Sun.
12. Uranus is the coldest planet in the solar system.
One of the most fascinating facts about Uranus is that it is the coldest planet in the Solar System despite not being the furthest away from the Sun. The lowest recorded temperature in the troposphere of Uranus was a bone-chilling -224°C (-371°F)!
13. Uranus gets its blue-green color from methane gas in the atmosphere.
The reason why Uranus has a blue-green hue is due to the trace amount of methane in its atmosphere which absorbs the red light from the sun but reflects the blue light back into space.
14. Uranus is one of the two so-called “ice giants.”
Along with its immediate neighbor Neptune, Uranus has been classified as one of the two so-called “ice giants” due to the abundance of ices in its atmosphere and mantle layer.
Below its heavy atmosphere, Uranus is made of layers of hydrogen, helium, and methane gases. They enclose a layer of water, ammonia, and methane – called “ices” above a small rocky core.
Uranus has no solid surface and more than 80% of the planet’s mass is made up of a hot dense fluid of these slushy “icy” materials deeper inside. However, the water in Uranus is not drinkable since the chemical reactions with the rock make the liquid water salty.
15. Uranus’s axis of rotation is tilted sideways, so its north and south poles lie where other planets have their equators.
Arguably the strangest of all Uranus facts is that it axis lies almost parallel to its orbital plane. To comprehend why this is so weird, it’s important to know that all planets in the solar system rotate on their axis with some level of tilt.
For example, Earth has an axial tilt of 23.44°. Likewise, Jupiter and Saturn are tilted by 3.13° and 26.73° respectively.
However, the axial tilt of Uranus is a staggering 97.77°, which is easily the largest axial tilt in the Solar System. Thus, while all the other planets resemble “spinning tops” as they orbit the Sun, Uranus rotates sideways and “rolls” like a ball as it orbits the Sun.
This is the reason why the north and south poles of Uranus lie near where the equator is on Earth and the other planets. Why is Uranus on its side?
The prevailing hypothesis is this extreme tilt was caused by a collision with an Earth-sized celestial body millions and millions of years ago, soon after Uranus formed. Until we know for sure, Uranus’s strange tilt will remain one of the greatest mysteries of the Universe.
16. Uranus has the most extreme seasons of any planet in the Solar System.
Just like on Earth, Uranus also experiences four seasons, however, each season on Uranus lasts 21 Earth years. Due to its extreme axial tilt (97.77°), Uranus has the most extreme seasonal variation of sunlight of all the planets.
For two 21-year seasons (winter-summer seasons) on Uranus, the poles of Uranus are pointed (more or less) either toward the Sun or away from it. During Uranus’s winter-summer seasons, one pole of Uranus plus virtually the entire section of that pole’s hemisphere is plunged into darkness and doesn’t see the Sun for 21 years. Meanwhile, the other pole of Uranus and a large section of that pole’s hemisphere of the planet have continuous daylight.
During the other two 21-year seasons (spring-autumn seasons) on Uranus, the rotational axis is oriented in such a way that the Sun shines on Uranus’s equator. Thus, both hemispheres go through a more “normal” day-night cycle (17 hours and 14 minutes) as the planet rotates.
17. All of the 27 known moons of Uranus moons are named after characters from the works of Shakespeare or Alexander Pope.
To date, 27 natural satellites of Uranus have been discovered. Interestingly, all the 27 moons of Uranus are named after literary characters from the works of William Shakespeare and Alexander Pope rather than characters from mythology.
The moons of Uranus are called Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda, Perdita, Puck, Mab, Miranda, Ariel, Umbriel, Titania, Oberon, Francisco, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos, and Ferdinand.
Though not as varied as those of Jupiter and Saturn, the range of Uranus’s moons is interesting. Uranus’s two largest moons, Titania and Oberon, are among the 10 largest moons in our solar system
18. Uranus’s moon Miranda is home to the tallest known cliff in the Solar System.
The Verona Rupes cliff on Uranus’s moon Miranda is estimated to be 20 km (12.4 miles) deep making it the tallest known cliff in the Solar System. Verona Rupes is more than 10 times the depth of the Grand Canyon.
Due to Miranda’s low gravity, it would take a human up to 12 minutes to fall to the bottom.
19. Uranus has 13 known rings.
To date, 13 distinct rings of Uranus have been identified. Uranus’s rings reflect only tiny amounts of light in the visible range, with more reflection in the infrared and near-infrared ranges. In fact, they’re so thin and dark, they weren’t even identified by astronomers until 1977.
The rings of Uranus are composed mainly of dark particles made of ice and rock. They are thought to be relatively young (not more than 600 million years old) and were probably created when one of Uranus’ old moons was destroyed by a comet or asteroid.
Due to its peculiar axial tilt of about 97.77°, Uranus’s rings are vertically inclined.
20. Only one spacecraft has flown by Uranus.
The only spacecraft to have flown by Uranus was NASA’s Voyager 2 spacecraft in 1986. It captured the first close-up images of the planet, its ring system, and its orbiting moons.
21. The wind speeds on Uranus can reach 900 km/h (560 mph).
Though not the windiest planet in the Solar System (that honor belongs to Neptune), Uranus experiences powerful zonal winds within its atmosphere that can reach up to 900 km/h (560 mph), and can generate anticyclonic storms comparable in size to North America like Jupiter’s Great Red Spot (known as the “Dark Spot”).
22. Uranus is the only Jovian planet not emitting excess internal energy.
One of the most bizarre facts about Uranus is that it is different from the other three Jovian giants (Jupiter, Saturn, and Neptune) in that it gives off significantly less heat than it receives from the Sun.
Because of their colossal sizes, all the Jovian planets were strongly heated during their formation by the collapse of surrounding material onto their cores.
In fact, Neptune, which is very similar in size to Uranus, produces approximately 2.6 times the amount of heat that it receives from the Sun. So, why is Uranus the only giant planet giving negligible internal heat?
It’s speculated that there either is some barrier preventing the internal heat from making its way to the planet’s surface or that Uranus was struck by a large body and helped disperse most of the heat that the other giant planets have retained. However, nobody really knows.
23. Neptune was identified as a planet because astronomers found oddities in the orbits of the Uranus.
After Uranus was discovered in 1781, astronomers noticed that the planet was being tugged slightly out of its normal orbit. Working independently of one another, John Couch Adams of Britain and Urbain Le Verrier of France predicted that the gravity from a neighboring and more distant planet beyond Uranus was affecting its orbit.
Employing mathematics, both Adams and Le Verrier figured out Neptune’s position in the 1840s. Finally, on September 23, 1846, German astronomer Johann Gottfried Galle discovered Neptune at almost exactly the position predicted by the calculations of Le Verrier.
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