10 Quick Facts about Uranus

10 Quick Facts about Uranus

It’s massive and cracked down the middle

1. Here are the facts.


Uranus is located at a distance of almost 20 AU from the Sun. It has a very long orbital period of 84 Earth years, although it only takes it over 17 Earth hours to do a full axial rotation. By volume, it is roughly the equivalent of 63,000 Earths, although only about 14,500 Earths by mass since it is a gas giant.

2. It’s got a weird name.

We’re not referring here about the double entendre that creates so many opportunities for jokes which we will, of course, be avoiding here (apart from the one above). Someone who is good at mythology should be able to spot it. Other planets, Mars, Jupiter, Saturn etc, these are all named after Roman gods. Uranus (well, Ouranos) was a Greek god. However, it could have been a lot weirder. Initially, its discoverer, Sir William Herschel, wanted to name it George, after King George III who was a big supporter of his efforts. More specifically, it would have been named Georgium Sidus (George’s Star).

Unsurprisingly, this decision wasn’t very popular outside of Britain so other options were proposed. For a while, Neptune was actually the frontrunner but we eventually settled on Uranus at the suggestion of Johann Elert Bode.

3. Herschel thought it was a comet.

William Herschel discovered Uranus. This was the first new planet discovered since Antiquity.

Naming a planet George’s Star would have been quite confusing but the truth is that, for a while, we weren’t sure exactly what Uranus was exactly. When he first discovered it in 1781, Herschel thought it was a comet or a nebulous star. According to his journal, he eventually ruled out a star and went to present his discovery to the Royal Society, but still touted it as a comet. Over the next few years, further observations allowed astronomers to conclude that Uranus was, indeed, a planet due to its almost circular orbit.

4. It is sometimes labeled an ice giant.

Although it’s still a giant ball of gases, there is quite a difference in the composition of Uranus (and Neptune) as opposed to Jupiter and Saturn. The latter two are mainly composed of hydrogen and helium – somewhere around 90% of their total composition. On the other hand, Uranus is composed of volatile ices, primarily water, ammonia and methane, thus being referred to as an ice giant. It still has hydrogen in its composition, but it is thought to lack the metallic hydrogen core that the gas giants have.

5. Let’s talk moons.

From left to right: Puck, Miranda, Ariel, Umbriel, Titania and Oberon

From left to right: Puck, Miranda, Ariel, Umbriel, Titania and Oberon

So far, we’ve discovered 27 moons orbiting Uranus, but none of them is particularly impressive. The largest satellite, Titania, is still about half the size of our own Moon. Other notable moons include Umbriel, Oberon, Ariel and Miranda. Even so, Uranus has the least massive satellite system of all the giant planets.

6. It gets pretty cold.

In fact, true to its name as an ice giant, Uranus is the coldest planet in the Solar System. You would expect the planet farthest from the Sun to be the coldest but actually Uranus has a colder atmosphere despite the two planets sharing a similar composition. Temperatures in Uranus’ atmosphere can get as low as -370 Fahrenheit (-218 degrees Celsius).

7. Uranus has rings.


Like we mentioned before, Saturn is not the only planet with rings even though its ring system is, by far, the most well-known and most visible. Jupiter also has rings and so does Uranus. The rings of Uranus are not very thick and very tricky to spot. So far we have identified 13 rings around the planet, although it is possible that more exist.

8. Uranus has a weird axial tilt.

It is almost 98 degrees, making the axis of rotation almost parallel to the plane of the Solar System. While the other planets rotate similar to a spinning top, Uranus’ rotation will be more similar to a rolling ball. This also means that each pole is exposed to the Sun for about half the year and then left in complete darkness for the other half; so each season on Uranus lasts roughly for 20 Earth years. There is only a thin strip around its equator that experiences the regular day-night cycle.

9. It has a dark spot.


Uranus doesn’t have particularly interesting weather anomalies like the Great Red Spot on Jupiter or the vortex on Saturn. Even so, it still has one thing which is a bit mysterious – a dark spot. It probably has more (Neptune has loads of them), but the spot in question was the first one discovered and we’re not really sure why it’s there. We’ve already talked about Uranus’ bizarre and extremely long seasons so the appearance of the spot could have something to do with the coming of spring in the planet’s northern hemisphere.

10. You can see Uranus with the naked eye.

With a brightness magnitude of about 5.3, it’s really at the limit of what we can see in the sky with our own eyes. However, you will need ideal conditions for this to happen. Here’s a rundown of what that means.


Want more? Here you go:

Moon  Mercury  Venus  Mars  Jupiter  Saturn  Moons