On this day in 1781, William Herschel discovered Uranus.
*pause for sniggers*
March 13th is a good day for astronomy and space exploration. In 1930 news of the discovery of Pluto was confirmed and telegraphed to the Harvard College Observatory, and in 1969 Apollo 9 returned safely to Earth after testing the Lunar Module - which would be used later that year for the Apollo 11 moon landing.
I feel a bit sorry for Pluto. It must be awfully confusing to be unsure whether you're a planet or not.