
1851 · 175 years ago
William Lassell discovers two new moons of Uranus
The English astronomer William Lassell discovered Ariel and Umbriel, two moons of the planet Uranus. They were only the third and fourth of its moons to be found. Umbriel is made mostly of ice mixed with rock, and has a very dark surface. Lassell was a mercha…