Today in History: The Discovery of Neptune on September 23, 1846.
Before this planet was actually seen at the Urania Observatory in Berlin, astronomers predicted its existence by using mathematics. We now know much about Neptune. Take a tour of NASA's site to learn more about the planet and the discovery that almost didn't happen...you may even discover that Neptune has the fastest winds in the solar system, has rings, storms, a dark spot, and many more interesting facts.
Nine Planets: http://nineplanets.org/neptune.html
Neptune on Wikipedia: http://en.wikipedia.org/wiki/Neptune