In 1781 British astronomer Sir William Herschel noticed something strange about the orbit of Uranus. Something was amiss. Uranus did not follow the laws of physics as he understood them at the time. Its movements acted as if something was disturbing it. Later in 1841 the french astronomer Alexis Bouvard also thought something was wrong with the orbit of Uranus. It is being tugged at by an unknown source. There had to be something out there that we don’t know.

During the 1840s astronomers John Adams and Urbain La Verrier independently decided to calculate using mathematics and physics where the mystery planet should be in the future to be seen. And that would explain the strange behavior of our seventh planet, Uranus.

September 23, 1846, acting upon Adams and La Verrier’s predictions, German astronomer Johann Galle made the very first direct observation of the blue planet at the Berlin observatory. It was there just like Adams and La Verrier predicted. It was dramatic and a sensation in the astronomical world because Johann Galle not only discovered Neptune, he also confirmed the “Newtonian Gravitational Theory.”

Johann Galle

It has been said that Adams and LaVerrier discovered a planet “with the point of a pen”

Because of its distance from the sun 4.5 Billion Kilometers, 30 AU, astronomical units , (30 times the sun earth distance) it takes Neptune 165 years to make one orbit and will not be back in this position until the year 2176.

July 12, 2011, Neptune arrived back to the spot “ heliocentric longitude” (relative to its orbit to the sun) were it was when it was discovered 165 years ago. And the planet still remains one of the biggest mysteries of the solar system.

In 1989 the Voyager 2 spacecraft flew approximately 3,000 miles above the north pole of Neptune returning many images of the planet before heading off for interstellar space.

In 2014 the “New Horizons” spacecraft will arrive for its visit of Neptune 25 years after Voyager. So it is said that July 12, 2011 is the birthday of the discovery of Neptune.

Interested in Astronomy? Come and learn.
Crossroads Astronomy Club meets at the University of Houston at Victoria, Room 223, West Building 7:00 p.m. every third Monday.
Star Party at Loblolly Ranch at Nursery Texas on July 29th. Contact KB Hallmark at 361-648-0089.