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Basics: Planet Uranus

in: The Solar System

Author: Zhunoman

Created: 11th Feb 2022 (Edited: 12th Feb 2022)

Tags: Space Planets Moons

This blue/ green planet is the first to have a known discovery date and discoverer. It is an ice giant, and it is about twice as far from the sun as its closest planet Saturn.

Key Info:

Date Discovered: 13 March 1781

Discovered By: William Herschel

Mass: 86,810,300,000,000,000,000,000,000 kg

Volume: 68,334,355,695,584 km cubed

Age: about 4.5 billion years

Diameter: 50,724 km

Basics: Planet Uranus

Main Image Credit: NASA/JPL, Published: December 18, 1986

Uranus is a bluish green planet named after the Greek god of the sky. Apparently there was some contention as to what it should be named. The person who found it, William Herschel, wanted to name it after King George 3rd. Like other planets though, the ancient god name was given. Although Herschel found Uranus, it was some time before it was realized it was indeed a planet. This was helped somewhat because of the observations of Johann Elert Bode.

This is the first planet that has a known date of discovery. This is because it is extremely hard to see with the naked eye, and would really need a telescope. It is almost 20 times further from the Sun than Earth.

Uranus has a unique orbit. It rotates seemingly on its side. In other, words its equator is almost at a 90 degree angle from the plane of its orbit. It is said to be like a rolling ball in its orbit around the sun.


Surface Features and Structure

Although Uranus may be similar to Saturn and Jupiter, it is referred to as an ice giant as opposed to gas giant. The other ice giant in the solar system is Neptune, which is slightly smaller but denser. Ice giants are distinguished from gas giants because of their differing composition. Whereas gas giants have large amounts of hydrogen and helium, ice giants have primarily heaver elements.

In a similar fashion to gas giants, it is difficult to define a surface as such. Deep down in the planet, there is likely to be a solid core. It is suggested that it would be covered with a very deep amount of water. It would be virtually impossible for there to be islands because the liquid level is so deep. This core is said to be as hot as 9000 degrees F (around 5000 degrees C).

When Uranus’ structure is being described it can sound somewhat odd. It is said to be about 80% “icy” materials, which are referred to as being dense and “hot!” This obviously sounds like a contradiction, in Earth terms, but it is another world with another type of structure. This is referred to as superionic water (or ice).


Atmosphere of Uranus

The outer atmosphere is composed mainly of hydrogen and helium. Note that, like gas giants, there is no true surface on ice giants, although there may be a dense solid core. This core will be deep under layers of liquid. It gets its blue/ green colour from methane gas, due to the way sunlight comes in and gets reflected back out.

The Voyager 2 probe did a flyby in 1986. It detected a giant dark spot and several other smaller spots. A few discrete clouds were noticed. Further study has shown dynamic clouds and very rapidly changing bright features. It is also known to have incredibly fast winds; some of these can reach 900 km per hour.

The following video is mostly for fun but describes what falling into Uranus would be like (hypothetically):


Rings of Uranus

Uranus does have rings, but nothing in the solar system is as pronounced as Saturn. Uranus has 2 sets of rings. They are somewhat faint, but it may be possible to view them with some powerful telescopes. Even the telescope company Celestron will warn that viewing may be less than interesting. Some telescopes may just show nothing but a boring green dot.


Moons of Uranus

Uranus has a large number of moons. 27 have been confirmed at the time of writing this blog entry. These have been named differently to other planets’ moons; they are named after characters in Shakespeare plays, and literary works from the poet Alexander Pope.

The inner moons seem to be half water and ice, but the outer ones are theorized to be captured comets. Like other big planets in our system, some of them are spherical while others are random shapes. The surface of all the main moons is only partially mapped. This was done via a flyby of the Voyager 2 spacecraft. Somewhere in the ball-park area of 35-40% of each main moon’s surface was imaged, with varying levels of mapping.

The following are the main 5 largest moons, in order of closeness to Uranus:

  1. Miranda: This is often called the Frankenstein moon because of its odd looking appearance. It looks as if it has been patched together from other moons. There are also odd surface features that make it look like an artist has carved shapes into it. 
  2. Ariel: This is the fourth largest of the Uranus moons. It is the most reflective of Uranus’ moons.
  3. Umbriel: This is the darkest of the planet’s moons. Like many other moons it is mainly ice, but it has a substantial amount of rock.
  4. Titania: This is the largest moon of the planet. It has long and prominent systems of “fault valleys”.
  5. Oberon: The outermost moon of Uranus, this moon is so far out it lies partially outside the planets magnetosphere. It consists of equal amounts of ice and rock.


Lawrence Sromovsky, University of Wisconsin-Madison/W.W. Keck Observatory, Published: 2004-July-11



Further Reading