| There is some controvery over the 1847 discovery dates of Ariel and Umbriel and this convoluted story is discussed in Alexander's book. |
| It was more than sixty years before the next two Uranian moons, Ariel and Umbriel, were discovered. |
| From their relative aspects in these respective positions I judge Umbriel to be about half as bright as Titania. |
| One suggestion is that another object struck Umbriel and shattered, generating dark fragments that later settled all over the surface. |
| Unlike other large Uranian moons, the surface of Umbriel has remained unchanged since the early times of the Solar System. |
| But Umbriel, one of Uranus' five large moons, doesn't fit the pattern. |
