Neptune was discovered on September 23, 1846 by Johann Gottfried Galle, of the Berlin Observatory, and Louis d'Arrest, an astronomy student, through mathematical predictions made by Urbain Jean Joseph Le Verrier. For more information you can visit: http://www.solarviews.com/eng/neptune.htm

The planet Uranus was discovered by the noted British astronomer, Sir William Herschel, on March 13, 1781. Actually, the planet had been observed numerous times by other astronomers as early as 1690, but it was thought to be another star. The planet was discovered accidentally while Herschel was surveying all stars down to magnitude eight -- those that are about ten times dimmer than can be seen by the naked eye. One "star" seemed different and within a year was shown to have a planetary orbit 18 times farther from the Sun than Earth. The new planet was named Uranus after the father of Saturn in Roman mythology. http://www.nasm.si.edu/etp/discovery/disc_planets.html Much like the discovery of Pluto, the search for a planet beyond Uranus began when mathematical calculations indicated that the orbit of Uranus did not behave in the way according to Newton's laws. Thus, astronomers concluded that there had to be a planet beyond Uranus because of a distortion in the planet's orbit. They were correct. On September 23, 1846, Johann Gottfried Galle (of the Berlin Observatory) and Louis d'Arrest (student of astronomy) became the first two people to observe the planet Neptune. They were successful not because they searched the entire heavens randomly, but by basing their observations around the area that Neptune was predicted to be. Urbain Jean Adams and Joseph Le Verrier had calculated where Neptune would be based on observations of Jupiter, Saturn and Uranus. It was fortunate that Galle and d'Arrest had scanned the skies within a small time margin from which the predicted locations were made. Neptune departs from the predicted orbit rather quickly and the planet would not have been found if the two astronomers had procrastinated (you see what could happen if you do?). After Neptune was discovered, the English and French battled over the right to name the planet, but in the end, credit for discovery was given to both sides. http://library.thinkquest.org/28327/html/universe/solar_system/planets/neptune/exploration/discovery_of_neptune.html Neptune was found when astronimers John Couch Adams and Urbain Jean Joseph Leverrier calculated the position of a new planet which they thought was altering the orbit of Uranus. When Neptune was first observed by German astronimer Johann Gottfried Galle in 1846. Even after the discovery of Neptune the orbits of Uranus and Neptune were still diferent from what astronimers thought they should be. This led to the search for yet another planet. The astronimers were surprised when they discovered Pluto, as they were expecting a planet much larger than the earth. But Pluto is only 3000km in diameter, smaller than what was previously thought to be the smallest planet in our solar system, Mercury. With the discovery of Pluto, both Uranus and Neptune are following their predicted path. http://neptune114.tripod.com/dis.htm The discovery of the planet Neptune remains notable because it resulted from theoretical prediction of the existence of a major solar-system body without previously seeing it. What led to its discovery was indirect evidence from the marginal disturbing effects which it produced gravitationally on the observed motion of its neighbouring planet (in order of orbital size) Uranus. The actual discovery was made on September 23, 1846 at the Berlin Observatory, by astronomer Johann Gottfried Galle (assisted by Heinrich d'Arrest), working from the mathematical predictions of Urbain Le Verrier which Galle had received just that same morning. It was a sensational moment of 19th century science and dramatic confirmation of Newtonian gravitational theory. In François Arago's apt phrase, Le Verrier had discovered a planet "with the point of his pen." Unfortunately, Le Verrier's triumph also led to a tense international dispute over priority, as shortly after the Galle/Le Verrier discovery, Astronomer Royal George Airy announced that British mathematician John Couch Adams had simultaneously made mathematical calculations similar to those of Le Verrier [1]. Before its discovery only seven major planets were known to astronomers, the furthest from the sun being Uranus. It was irregularities in the orbit of Uranus that led Adams in England privately and Le Verrier in France publicly to predict an eighth planet. It also led a British team to embark on a secret and ultimately unsuccessful race for its discovery, before Le Verrier's published predictions could be acted upon by anyone other than a British astronomer. http://en.wikipedia.org/wiki/Discovery_of_Neptune I hope this is helpful.

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