The 8th planet was discovered 65 year later. Neptune discovery is rather impressive example of the power of the scientific method. Modern studies of Galileo’s notebooks show that he saw Neptune on December 24, 1612, and again on January 28, 1613 but he plotted it as star in the background of drawing Jupiter.
In October 1845, young English astronomer John Couch Adams going through a laborious and difficult calculation computed the orbit of the undiscovered planet. He sent his prediction to the Astronomer Royal, Sir George Airy, who passed it on to an observer who began a painstaking search of the area star by star. Adams predicted position was almost as good, off by less than 1.5°.
Meanwhile, the French astronomer Urbain Jan Leverrier made the same calculation and sent his prediction position of the planet to Johann Galle at the Berlin Observatory.
Galle received Leverrier’s prediction on the afternoon of September 23, 1846 and after searching for 30 minutes that evening, found Neptune. Neptune was nearly the exact size, in appearance, as predicted by Leverrier and was less than 1° from the position predicted for it by Leverrier.
Little was known about Neptune before the Voyager 2 spacecraft swept past it in 1989. Voyager 2 passed only 4900 km above Neptune’s cloud tops, closer than any spacecraft has ever come to one of the Jovian planets.
Discovery of Neptune
