This Day in History (13-Mar-1781) – William Herschel Discovers Uranus

On March 13th, 1781, astronomer Sir Frederick William Herschel announced the discovery of Uranus.  The interesting part of this story is that we already knew about Uranus. It was up there, drifting dimly, one of the few planets visible to the naked eye — just barely, if you knew where to look. English astronomer John Flamsteed noticed it almost one hundred years prior, but we always just assumed it was a star.

It wasn’t until Herschel did a survey of all stars down to a magnitude eight — those significantly dimmer than can be seen by the naked eye — that he noticed one that was a little off. He assumed it was a comet. He observed the object for 4 years. It moved differently, but it did lack a tail. The others he told about his findings believed it was a planet long before he did, but Herschel  is still credited with finding it.

Herschel argued with other astronomers over the new planet’s name. He wanted to name it after King George III of Great Britain while others wanted him to name it after himself. Finally, they chose to name it like the other planets– after an ancient god. Uranus was named after Ouranos, one of the first gods in Greek mythology. Previous planets were named after Roman Gods.

Although Herschel discovered two of the planet’s satellites, most of the rest were spotted by Voyager II. The total number of moons for Uranus is 21, the largest number for any planet in our solar system.  In 1977, scientists from Cornell University watched as Uranus appeared to blink several times. They later realized the blinking was caused by a band of rings surrounding the planet. These rings are very dark and narrow, unlike Saturn’s, which are bright. Voyager II sent back many pictures that clearly show these rings.

On this day in 1930, Pluto’s discovery was also announced. They’d known about it for almost a month by then, but they held off talking up the then-9th-planet to coincide with Uranus’s 1781 debut.

Reference:

http://www.geekosystem.com/tigh-herschel-discovers-uranus/

http://www.optcorp.com/articles/sir-william-herschel-discovers-uranus/

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