Neptune was discovered by John Couch Adams in 1846.
Adams was an English astronomer and mathematician who, at the
age of 24, was the first person to predict the position of a planetary mass beyond Uranus.
Pluto was discovered by astronomer Clyde Tombaugh in 1930. A 9th planet had been looked for some time.
It was believed that such a planet had to exist in order to explain some odd things happening in the orbits of Uranus and Neptune.
Only 3 of the 9 planets in our solar system have official "discoverers" and "times of discovery."
The reason is simple - all of the other planets are easily seen by the unaided human eye.
This means that humankind has been looking at these objects (whether they understood what they were or not)
since first gazing at the night sky!
Uranus was discovered by Sir William Herschel in 1781. Herschel was probably
the most famous astronomer of the 18th century. In addition to discovering the planet
Uranus, he also observed and cataloged over 800 double stars and 2,500 nebulae.
He was the first astronomer to correctly describe the spiral structure of our Milky Way Galaxy.
Edmund Halley proves that comets orbit the sun like the planets and successfully
predicts the return of Halley's Comet. He determines that comets seen in 1531 and 1607 are
the same object following a 76-year orbit. Halley's prediction is proven in 1758 when the comet returns.
Unfortunately, Halley had died in 1742, missing the momentous event.
Edwin Hubble determines the distance to many nearby galaxies and discovers that the farther they are from us, the faster they are flying away from us. His calculations prove that the universe is expanding.
Astronomers find a host of extra solar planets as a result of improved telescope technology and prove that other solar systems exist, although none as yet resembles our own. Astronomers are able to detect extra solar planets by measuring gravitational influences on stars.
Unexpectedly, astronomers find that instead of slowing down due to the pull of gravity, the expansion of the universe at great distances is accelerating. If these observations are correct and the trend continues, it will result in the inability to see other galaxies. A new theory of the end of the universe based on this finding has been called the "big rip."