The eighth planet is named after the Roman god of the oceans.
Of the eight planets in our solar system (Pluto is no longer considered a planet), only Neptune is not visible to the naked eye. However, two scientists independently guessed the planet's existence and position almost simultaneously.
Planetary Drift
After Sir William Herschel discovered Uranus in 1821, the astronomer Alexis Bouvard calculated its predicted orbit; however, Uranus' path did not quite match Bouvard's charts.
A More Distant World
Two astronomers -- John Couch Adams from Britain and Urbain Le Verrier from France -- posited that the inaccuracies in Bouvard's charts were due to Uranus being influenced by the gravity of a more distant planet. They independently produced calculations predicting the planet's position.
Neptune's Discovery
On September 23, 1846, La Verrier sent his calculations to a Berlin observatory where astronomer Johann Gottfried Galle turned his telescope to the night sky and located the new planet within just one degree of La Verrier's prediction. Adam's prediction was within 20 degrees and both scientists were awarded credit for Neptune's discovery.
Tags: Bouvard charts
