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The discover of the Neptune in 1846 by John Couch Adams and Urbain Leverrier is a prime example of "if you can't make the scientific theory fit the Universe, than make the Universe fit the theory". By the middle of the nineteenth century, the theory of planetary motion, first developed by Kepler and Newton, was well advanced.
It worked remarkably well for all the planets except Uranus, which seemed to violate Newton's laws of motion. Rather than modify the scientific theory, it was easier to change the Universe by adding another planet to the Solar System. Fortunately for all concerned, this planet, after a good deal of searching, was actually found. The orbit of Neptune is 30.1 a.u. from the Sun and it takes over 165 years to complete one revolution around the Sun.
Neptune's motion as seen from the Earth is similar to that of Uranus. It moves forward for about half the year and the retrograde for the next half. Neptune can only be seen with the assistance of binoculars or a telescope and appears as a small green disk. It has eight known satellites, one of them quite large, but the planet is so distant from us that there is little to see except its disk. Through binoculars, it may appear as just another dim star. To find this distant planet, you will need a star chart of the area. Once you familiarize yourself with all the dim stars within the area, it will be possible to identify the intruder Neptune as a planet.