Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

April 7, 1996

Uranus's Moon Umbriel: A Mysterious Dark World
Credit: Photo Credit: NASA, Voyager 2

Explanation: Why is Umbriel so dark? This dark moon reflects only half the light of other Uranus' moons such as Ariel. And what is that bright ring at the top? Unfortunately, nobody yet knows. These questions presented themselves when Voyager 2 passed this satellite of Uranus in January 1986. Voyager found an old surface with unusually large craters, and determined Umbriel's composition to be about half ice and half rock. Umbriel is the fourth largest and third most distant of Uranus' five large moons. Umbriel was discovered in 1851 by William Lassell.

Tomorrow's picture: Uranus's Moon Oberon: Impact World

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U.