William Shakespeare and Alexander Pope probably never imagined, in their wildest flights of fancy, that their characters' names would ever grace the moons of a planet billions of miles away. Carving a path through the remote expanses of our solar system, that planet is Uranus – meaning God of Air – and around it orbit 27 moons.
Although that sounds like an impressive number, Jupiter has a record-breaking 63 moons. However, what makes Uranus unique is not the number of satellites encircling it, but their names. While other planets' moons are named after Greek or Roman mythological figures, the moons of Uranus are named after literary characters from the works of Pope – and Shakespeare, in particular. They span plays including "A Midsummer Night's Dream," "The Tempest," "King Lear," "Hamlet," "The Taming of the Shrew," "Troilus and Cressida," "Othello," "Romeo and Juliet," "The Merchant of Venice," "As You Like It," "Much Ado About Nothing," "The Winter's Tale" and "Timon of Athens."
Oberon and Titania – the largest of Uranus' moons – were the first to be discovered in 1787, by renowned astronomer William Herschel. He recognized that they were moons, not stars, and, to honor his British heritage, named them after characters in Shakespeare's "A Midsummer Night's Dream." This set a precedent for not only naming the moons of Uranus after literary characters, but naming all moons – and moons yet to be discovered – after fictional figures populating literature.
In addition to paying homage to Shakespeare, Titania is the largest of the planet's moons, with a diameter of 981 miles, and is the eighth largest moon in the entire solar system. It's approximately 20 times smaller than the Earth's moon. Herschel believed that he'd discovered several more Uranian moons, but other astronomers were unable to confirm these sightings.
William Lassell, who had been the first to observe a moon orbiting Neptune, discovered the next two of Uranus' moons, Ariel and Umbriel – named after characters from Alexander Pope's "The Rape of the Lock." It would be nearly a century before American astronomer Gerard Kuiper discovered another moon in 1948 and named it Miranda – a moniker culled from Shakespeare's play, "The Tempest."
Then everything changed when the Voyager 2 spacecraft journeyed to Uranus in 1986 and discovered an additional 10 small moons, each with a circumference of only 16 to 96 miles. These moons were Juliet, Puck, Cordelia, Ophelia, Bianca, Desdemona, Portia, Rosalind, Cressida and Belinda.
After the Voyager 2 mission, astronomers used the Hubble Space Telescope for studies of Uranus, raising the total of the planet's known moons to 27. This is no small feat – some of the moons are barely 8 to 10 miles across and tar black. And they're almost three billion miles away.
Scientists have categorized the moons of Uranus into three groups – inner moons, major moons and irregular moons. The 13 inner moons – small, dark bodies that share common properties and origins with the planet's rings – are Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Cupid, Belinda, Perdita, Puck and Mab, and were observed by Voyager 2. They are much farther away from Uranus than the major moons.
The planet's large moons, known as its major moons, are Miranda, Ariel, Umbriel, Tatania and Oberon. These moons are substantial enough to have achieved increased temperature caused by gravitational pull, and internal processes that create canyons and volcanoes on their surface. The structure of the moons beyond Oberon's orbit remains a mystery, but they are probably asteroids captured by Oberon's gravitational field. Rock and ice comprise all of the major moons except Miranda, which is completely icebound.
Uranus also possesses nine irregular moons. Along with the 13 inner moons, these were not discovered until the Voyager's missions. The irregular moons are considerably farther from Uranus than the major moons are, and include Francisco, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos and Ferdinand. These have elliptical and retrograde orbits – they orbit Uranus in the opposite direction from the regular moons and from the planet's rotation.
Little did Shakespeare and Pope know that their works would not only affect the earth, but would powerfully impact the farthest reaches of the solar system itself.