The Moons of Uranus
The planet Uranus has many fascinating worlds that orbit it. There are likely still other moons of Uranus that have yet to be discovered. Since Uranus rotates on its side, its moons also rotate up and over the planet in the same direction.
As you read about each of these fascinating worlds, you will notice that many were discovered by a satellite called Voyager 2. Because Uranus is so far away it is almost impossible to see its smaller moons from Earth. They could not be discovered until a satellite was sent in 1986 to explore Uranus close up.
Uranus has 27 moons. Five of these worlds are large, while the rest are much smaller. Most of the small moons are probably captured asteroids or comets which wandered too close to Uranus. Like the other gas giants, Uranus has a system of rings. Some of the smaller moons are responsible for shepherding those rings. These Shepherd moons orbit at the edges of the rings, and keep any dust or ice from escaping.
How did the Shepherd moons end up at the edges of the rings?
That is a good question. When these moons were first captured, or first formed, they were not at the edge of the ring. There may not even have been a ring at all. Over millions of years, the dust and ice on the outside of the moons was aloud to escape, while the dust and gas on the inside, or between the moons, was not. In other words, the rings formed in the places where the moons were already orbiting.
What would have happened if the shepherd moons had been further apart or closer together?
If the shepherd moons had been further apart, the ring would have been wider. If the moons were closer together, then the ring would have been more narrow.
Uranus has ten moons which lie closer to the planet’s surface than the other moons. We call these worlds the Inner Moons.
CordeliaThe closest moon to the surface of the planet Uranus is Cordelia. Cordelia was discovered by Voyager 2 in 1986. It appears that this moon is a shepherd moon for Uranus’ Epsilon ring. A shepherd moon is a moon that orbits a planet on the edge of its rings. By orbiting on the edge of the ring, the moon keeps the dust and ice inside of the ring, much like a shepherd keeps sheep inside a field.
In Shakespeare’s play King Lear Cordelia was a daughter of King Lear.
OpheliaOphelia is the second of Uranus’ moons. This world orbits just outside the Epsilon ring, and for this reason is believed to be, like Cordelia, a shepherd moon.
Ophelia, which was discovered by Voyager 2 in 1986, was named after the daughter of Polonius in Shakespeare’s Hamlet.
BiancaBianca was discovered by Voyager 2 in 1986. It is a small icy world, and like many of Uranus’ moons, probably a captured asteroid or comet.
Bianca was named after the sister of Katherine in Shakespeare’s Taming of the Shrew.
CressidaThe fourth of Uranus’ moons is the world Cressida. Cressida was discovered in 1986 by Voyager 2.
Cressida is the daughter of Calchas in Shakespeare’s play Troilus and Cressida.
DesdemonaDiscovered in 1986 by Voyager 2, Desdemona is the fifth of Uranus’ moons.
Desdemona is the wife of Othello in Shakespeare’s Othello.
JulietJuliet is the sixth moon from the surface of Uranus, and was discovered by Voyager 2 in 1986.
This moon was named after the young girl in Shakespeare’s play Romeo and Juliet.
PortiaUranus’ seventh known moon is the world Portia. Portia was discovered in 1986 by Voyager 2.
Portia was a rich woman in Shakespeare’s Merchant of Venice.
RosalindRosalind is the eighth moon from the surface of the planet Uranus. It was discovered in 1986 by Voyager 2.
Rosalind is a daughter of the banished Duke in Shakespeare’s play As You Like It.
BelindaDiscovered in 1986 by Voyager 2, Belinda is the ninth of Uranus’ moons.
Belinda is named after the heroine in Alexander Pope’s The Rape of the Lock.
PuckThe tenth of Uranus’ moons is Puck. Puck was discovered in 1986 by Voyager 2.
Puck is a fairy in Shakespeare’s Midsummer Night’s Dream.
MirandaThe eleventh of Uranus’ moons is the world Miranda. Miranda is a very interesting world. It is made up half of rocky material, and half of ice. In one place Miranda has a huge cliff that is 5 km (3.1 miles) high. Miranda was discovered in 1948 by Kuiper.
This icy world was named after a daughter of the magician Prospero in Shakespeare’s The Tempest.
ArielDiscovered in 1851 by William Lassell, Ariel is the twelfth moon in Uranus’ system. As you can see by looking at the picture, Ariel is made up of a system of large interconnecting valleys. These valleys probably formed as Ariel froze and cracked. The smooth surface of this world tells scientists that it has been re-surfaced sometime in the recent past.
Ariel was a spirit in Shakespeare’s The Tempest.
UmbrielUmbriel’s heavily catered surface gives scientists a lot of information about this world. It means that Umbriel has not been resurfaced for a long time, probably since it was first formed.
Re-surfacing is when the old surface of a world is covered up by a new surface. This happens on Earth by volcanic eruptions. Re-surfacing can sometimes happen if a hot object hits a world. That object might melt the surface, forming a new smoother surface in its place.
TitaniaDiscovered in 1787 by William Herschel, Titania is the largest of Uranus’ moons. It is believed that long ago Titania had a huge liquid water ocean. As Titania cooled, the surface froze over. Later as the interior froze, the surface expanded and cracked. These cracks formed the giant valleys found on Titania today.
Titania is the Queen of the Fairies in Shakespeare’s Midsummer Night’s Dream.
OberonUranus’s fifteenth moon and second largest is Oberon. Oberon was discovered in 1787 by William Herschel. Early in Oberon’s history it was a very active world, but today it is frozen solid. Oberon is about half rock, and half frozen water.
Oberon is the husband to Titania and the King of the Fairies in Shakespeare’s Midsummer Night’s Dream.
The other moons of Uranus are Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos, Mab, Pertida, Cupid, Francisco and Ferdinand. We are still learning about these worlds.