October 24, 2011 - Ariel and Umbriel Discovered


– 1851

William Lassell was apprenticed to a merchant in Liverpool, England, and then he made a fortune as a beer brewer. But he is known for his hobby.

Some hobby!

Lassell was interested in astronomy, and, remember, he made a fortune, so he had plenty of money. He was able to build an observatory near Liverpool, and he himself ground and polished a 24-inch mirror for its telescope. He was the first to use a particular “equatorial mount” to easily track objects in the sky as the earth rotates. (Remember, although all the stars and planets seem to cross the sky as the night passes, it is really the earth spinning that creates this apparent motion.)

Using his telescope, Lassell discovered Triton, the largest moon of Neptune—just 17 days after Neptune itself was discovered! That was in 1846. In 1848, he discovered Hyperion, a moon of Saturn (although on the same night, another astronomer independently made the same discovery). Finally, on this day in 1951, Lassell discovered two new moons of Uranus.

Uranus and its rings and moons...
Its axis of rotation is tipped so that
its north and south pole are where
most planets' equators are...
Uranus's moons (we now know of 27!) are named after characters from the works of Shakespeare and Alexander Pope. Ariel is a sky spirit in Shakespeare's The Tempest, and Umbriel is a character in a poem by Alexander Pope.

By the way...

In case you think that William Lassell spent his entire fortune on building an observatory and telescope...no, not so much. In 1855 he built another telescope, this one twice as large, and had it installed in Malta, in the Mediterranean, where the weather and therefore skies are better for observation. When he died in 1880, he still left a fortune equal to millions of U.S. dollars of today!

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