Titania is Uranus’s largest moon. It takes its name from a character in the William Shakespeare play A Midsummer Night’s Dream. All of Uranus’s 27 moons are named from characters in plays, either those of Shakespeare or of Alexander Pope.
– Physical Characteristics –
Titania orbits Uranus farther out than most of the planet’s other large moons, but still within the range of its magnetic field. Like many moons in the solar system, the planet is tidally locked, meaning that both its period of rotation (one Titania “day”) and its period of orbit around Uranus last the same amount of time, about 8.7 days. The same process affects Earth’s own Moon, although in the Moon’s case, both last about one month. As with our moon, this process means that if from the perspective of an observer in Uranus’s atmosphere, Titania would always present the same face to the planet.
Unlike the Moon, however, but much like other moons at this distance from the Sun, Titania is made up of an even mix of water ice and rock. This is actually somewhat unusual in the outer solar system, where moons tend to have more ice than rock in their internal makeup. The planet’s surface is pitted not only with impact craters but long, deep rifts. There are some theories that Titania’s interior includes not only a rocky core but, at some level, a liquid water layer resembling an underground ocean. Several moons of Jupiter and Saturn may also have such oceans, although none are as substantial as that of Jupiter’s moon Europa. It appears to have a very thin atmosphere of carbon dioxide.
– Discovery and Exploration –
Titania was discovered by 18th-century British astronomer William Herschel in 1787, along with the next-largest moon orbiting the planet, now known as Oberon. The two most distant gas giants, Uranus and Neptune, were difficult to study from Earth (Neptune itself was not discovered until later, with the aid of mathematical predictions based on theories of gravity), and it took quite some time for other astronomers to confirm Herschel’s discovery. (Several other Uranian moons which Herschel claimed to have discovered were never confirmed at all, and were probably either errors or deliberate fraud.)
To date, there have been no space probes sent specifically to Uranus or its moon system, so astronomers’ understanding of Titania is still frustratingly limited. No future space probes to Uranus are on the drawing board yet, either. For the foreseeable future, therefore, the only relatively close-up images of Titania are a series of pictures taken by Voyager 2 in the 1980s, from a distance of about 350,000 kilometres (about 220,000 miles), or roughly the distance from the Earth to the Moon.