Did you know that Uranus was (accidentally) discovered on this day in 1781, the first planet to be discovered with the aid of a telescope? At first, British astronomer William Herschel thought the object in the sky to be a star or comet, but within two years, other astronomers showed it was a new planet orbiting the Sun. The ice giant is four times wider than the Earth and appears blue due to the methane in its atmosphere. Photo: NASA