You know the difference between inventions and discoveries, don’t you? While both of them are fundamental processes that have shaped the course of human history, there’s a difference between them. In simple terms, inventions correspond to coming up with something new based on experimentation and study. Discoveries, meanwhile, are the process of finding something that already exists, especially for the first time.
When we speak of Ariel and Umbriel, two of Uranus’ many moons (29 officially as of August 2026), it is their discovery that we talk about. This is because these satellites have existed for a very long time, and it was only their existence that was revealed in reality when English astronomer William Lassell discovered them.
Shakespeare has a say
The naming conventions of celestial bodies can be a topic unto itself. There’s a fair bit of mythology involved, with planets in our solar system bearing names reflecting mythological characters. As for their satellites, it was either named after mythological figures related to the planet’s namesake, or had literary links. In the case of Ariel and Umbriel, it was the latter.
Following his discoveries, Lassell requested Sir John Herschel to name these two moons. It is worth noting that John was the son of Sir William Herschel, the discoverer of the planet Uranus. John decided to name both satellites based on the works of English poet Alexander Pope and English playwright and poet William Shakespeare.
Both Ariel and Umbriel are names that appear in Pope’s “The Rape of the Lock” and the former appears in Shakespeare’s “The Tempest” as well.
Umbriel is named for a malevolent spirit in the 18ᵗʰ Century poem. While Ariel is a sylph who narrates the poem in Pope’s work, the character is a spirit who serves a magician in Shakespeare’s work. The magician, Prospero, rescues Ariel from a tree in which he had been held in prison by Sycorax, a witch. Incidentally, both Prospero and Sycorax were also chosen as names for other satellites of Uranus.
Born in Bolton, England on June 18, 1799, Lassell belonged to a family that was fairly well-off. The boy born close to the turn of the century turned into a teen who moved from Rochdale, Manchester to Toxteth, Liverpool in 1815. Here, he apprenticed in a local merchant’s office until 1822. His life was just about to hit the fast-forward button.
Beer brewer turns astronomer
He set out as a beer brewer on Milton Street in Liverpool by November 1824 and business soon flourished. Riches led him to leisure, leisure lent him time, and time turned into newfound interests. Astronomy turned out to be the unexpected beneficiary due to the wealth that he accumulated.
Portrait of William Lassell. | Photo Credit: Wikimedia Commons
He made so much money that he was able to build an observatory at his own home! By the summer of 1839, ‘Starfield’ on West Derby Road was established with a 9-inch diameter telescope that Lassell built on his own. This only served to whet his appetite and he paid a visit to Irish engineer and astronomer William Parsons, 3ʳᵈ Earl Rosse. Lord Rosse was the designer of the Leviathan of Parsonstown, the largest telescope of the time — a record it held into the next century.
The Grand Amateurs
Returning to Liverpool with more knowledge of the subject, Lassell went on to build a successful partnership with two others. Fellow English amateur astronomer William Rutter Dawes also had his own observatory in Ormskirk, and he had a keen eye for testing calibrating telescopes. James Nasmyth, a Scottish engineer and the inventor of the steam hammer, turned to astronomy following retirement from business as a mechanical engineer. All three of them — Lassell, Dawes, and Nasmyth — were recognised as the “Grand Amateurs” of astronomy.
The trio built a telescope with a diameter of 24 inches that was constructed in Lassell’s workshops at Starfield. The 20-foot-long tube with a mirror that ran two feet across was polished using a machine of Lassell’s own design and was the first telescope of its size to achieve equatorial mounting. This enabled them to not only track down specific objects, but also observe and follow them for a longer period. The discoveries were just around the corner.
Four moons in five years
In a period of five years, Lassell discovered four satellites in the solar system using this telescope. The first of these discoveries took place on October 10, 1846, when Lassell discovered Triton. The largest of Neptune’s satellites was discovered by Lassell just 17 days after Neptune itself had been discovered! If Neptune were the size of a basketball, then Triton would be as small as a bead that is one-and-a-half centimetres across — an indicator of how good Lassell’s telescope was.
This image taken by Voyager 2 in 1986 shows Umbriel, one of the two moons of Uranus that Lassell discovered. | Photo Credit: NASA / Wikimedia Commons
In 1848, Lassell discovered Hyperion, the largest of Saturn’s irregular, non-spherical moons. Lassell shares this discovery with William Cranch Bond and his son George Phillips Bond — an American father-son duo who independently discovered the same moon.
On October 24, 1851, Lassell doubled the number of satellites he had discovered from two to four. Using the same telescope that had yielded success, Lassell discovered Ariel and Umbriel. The discovery of these two new moons of Uranus added to the two moons (Titania and Oberon in 1787) that had already been discovered shortly after the planet itself had been discovered in 1781.
An eventful October
In addition to the discovery of Ariel and Umbriel, October 1851 turned out to be special for Lassell for another reason as well.
In case you are wondering what could be more special than discovering two moons, it was the chance of meeting someone whom you don’t get to meet easily.
In October 1851, Queen Victoria made a visit and tour of Liverpool. Lassell’s astronomical work was so highly regarded that he was apparently the only person to meet the Queen by her own request.
In the years that followed, Lassell made more observations, built a third and final great telescope (a Newtonian Reflecting Telescope that was 48 inches wide and 37 feet long), and did some back and forth between Liverpool and Malta in search of better viewing conditions. His contributions naturally led to a number of recognitions. He won the Royal Astronomical Society Gold Medal in 1849 and went on to serve as the society’s president between 1870 and 1872. He was also elected as a fellow of the Royal Society in 1849 and was awarded the Royal Medal in 1858. Belonging to the last generation of great amateur astronomers, Lassell had done everything that he could before his death in 1880 to set the stage for the professional astronomers to take over.