Short answers, pulled from the story.
William Lassell discovered Umbriel on the 24th of October 1851 while observing from his observatory in England. This event marked the first confirmed sighting of these distant worlds since the invention of the telescope.
The name Umbriel comes from Alexander Pope's poem The Rape of the Lock written in 1712 where it describes a dusky melancholy sprite. The Latin root suggests darkness or shadow fitting for a world far from the Sun.
Umbriel takes about 4.1 Earth days to complete one full circle around the planet. Its orbital period matches its rotational period exactly locking one face toward Uranus forever.
The density of Umbriel measures 1.54 grams per cubic centimeter indicating it consists mainly of water ice mixed with rock and carbonaceous materials. About 40% of its mass comes from dense non-ice components including heavy organic compounds called tholins.
Voyager 2 photographed Umbriel during its flyby of Uranus in January 1986 at a distance of approximately 295,000 kilometers. These pictures cover only 40% of the total surface area available for study with spatial resolution around 5.2 kilometers.