Who discovered Neptune?

Most discoveries are straightforward. We can clearly say who discovered it and when. But there are exceptions, where it is not sure who discovered it first. And the discovery of Neptune is one of them.

Following the discovery of Uranus, astronomers realized that Uranus had been plotted in star charts almost a century before it had been discovered by William Herschel. But when these data was analysed it was evident that something was tugging Uranus while it orbited around the sun.

Berlin Observatory

One astronomer who use the data to calculate the position of this unseen planet was English astronomer John C Adams. He calculated the orbit and position of this planet by October 1845. But his calculations and predictions were not taken seriously.

French astronomer Urbain Jean Leverrier also made calculations of his own and predicted the position of the eighth planet, almost an year later in September 1846. Based on his predictions, Johann Galle of Berlin Observatory discovered Neptune on the same day. The position was only 2° away from John C Adams's predicted position.

So the credit of discovering Neptune goes to three astronomers, John C Adams, Urbain Jean Leverrier and Johann Galle.

But to make things more complicated, Galileo's notes have recorded Neptune close to Jupiter on two occasions. But during that period Nepture had begun its retrograde motion, so it would have been difficult to detect any noticeable movement against the background stars. Although Galileo was the first person to observe Neptune, he failed to identify it as a planet.

To test your knowledge on discovery and other aspects of Neptune, take the Neptune Quiz 

Or learn more about the planet with Neptune (True Books)