||50 x 36 x 36
||54 x 38 x 38
||64 x 46 x 46
||92 x 74 x 74
||90 x 54 x 54
||150 x 74 x 74
||156 x 126
||128 x 64 x 64
||10 (or poss. 25)
A collage of Voyager 2 photographs showing the major moons of Uranus in correct relative sizes. From left to right: Puck, Miranda, Ariel, Umbriel, Titania and Oberon.
Solar System -
A schematic (to-scale) of the ring & moon system of Uranus
Uranus has 27 identified moons to date, three of which (Ariel, Umbriel & Belinda) are named from a poem by Alexander Pope, while the remainder are named after characters from Shakespeare. The table to the right lists the moons in order from Cordelia, closest to Uranus, outwards with their diameters in kilometers. The smaller moons are, as usual, far from spherical, but the measurement indicates a nominal diameter. Where available, I have linked to photographs of the moon.
The thirteen moons out to the newly-discovered (in 2003) Mab are considered "inner moons". They are all orbiting within the ring system, and some, Cordelia & Ophelia, for example, act as "shepherd moons" keeping the rings in place. The orbits of these moons are fairly chaotic and, over millions of years, the orbits cross each other, leading to the risk of collisions. This may well be how the rings originated. These moons formed from an accretion disk that was either present when Uranus formed, or resulted from the possible collision event Uranus suffered which tilted it so far on its axis.
The next five moons are the largest. Miranda is made primarily of ice, probably including ammonia and carbon dioxide. The other four are roughly half ice and half rock, with rocky cores covered with an ice mantle. While all five are cratered, all but Umbriel show signs of geological activity that has resurfaced the planet in the past.
The nine outer moons are all small and irregular, and are almost certainly captured objects. Unlike all the other moons, the outer moons, except Margaret, have retrograde orbits. Margaret's orbit, while prograde, has a large eccentricity.
The four largest moons make up 99.2% of the mass of Uranus' moons system. Miranda is a further 0.7% while the remaining 22 moons make up barely 0.1%. Oberon, the furthest of the large moons from Uranus, orbits about 583,500 km (365,000 miles) from Uranus. There is then a huge gap until we reach Francisco which orbits some 4,276,000 km (2,672,000 miles) from Uranus, with Ferdinand out at 20,900,000 plus km (13,060,000 miles).
This montage shows Uranus and its five major moons. The images are from the Voyager 2 spacecraft. As shown here, the moons, from largest to smallest, are Ariel, Miranda, Titania, Oberon and Umbriel.
Wikipedia has an excellent table with information about all of Uranus' Moons. NASA also has more information on Uranus' Moons.
Uranus' Moons - Characteristics
All sizes are approximate. Orbits are the average distance to Uranus; the semi-major axis. Negative periods, shown in italics, represent those satellites having retrograde orbits. All the irregular moons from Francisco outwards have retrograde orbits except the tiny moon Margaret. Most of the inner orbits, Cordelia to Oberon, have low eccentricity (less than 0.0025). Francisco to Trinculo are somewhat more eccentric, while the outer four are highly eccentric in the range of about 0.37 to 0.66.