Neptune is the farthest planet from the sun (sorry, Pluto) and was discovered in September 1846. I thought it was interesting that it was the first planet that was discovered because we were looking for it rather than by accident. Astronomers suspected it was there because of Uranus’ orbit. Galileo may have observed it in 1612-13 but did not recognize it as a planet.
We don’t know much about Neptune, but we do know it is 17 times as big as the Earth but less dense. It’s covered in blue methane clouds and has 13 moons. It has rings, but they are less substantial than Saturn’s.