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pseudoastro.wordpress.com — Finding Uranus
Until 1781, the solar system was known to consist of Earth, Venus, Mercury, Sun, Mars, Jupiter, and Saturn, along with the moon, some other moons, and some unexplainable and unpredictable comets. That was it, and it wasn’t until William Herschel observed a ball-like object (not star-like) moving among the fixed background stars.
It took two years for Herschel to admit that he had really discovered the first planet in recorded history. But since it was discovered after Newton created Calculus and Kepler the Laws of Planetary Motion, various astronomers and mathematicians were able to observe it and predict its orbit based on its distance from the sun and the gravitational interactions with other planets.
The First Planet X
One of these people was Alexis Bouvard, who published tables of dates and coordinates that predicted where Uranus should be at a given time. These were based on the known laws of physics. But, Uranus refused to follow Bouvard’s tables.
In 1843, John Couch Adams (from Britain) calculated the orbit of a hypothesized eighth planet that could account for Uranus’ odd orbit. But no one really seemed to care about this undiscovered Planet X.
Two years later, a Frenchman by the name of Urbain Le Verrier did the same thing, but more precisely. Again, no one seemed to care. That was until Le Verrier sent his calculations to the Berlin Observatory’s astronomer Johann Gottfried Galle. A then-student at the observatory, Heinrich d’Arrest, convinced Galle to look for it.
That evening, September 23, 1846, Galle looked for this mysterious planet, responsible for Uranus’ weird orbit, and he found the planet within 1° of where Le Verrier thought it would be (for reference, the moon on the sky is 0.5°). This was within 12° of where Adams thought it should be.
At the time, there was no real debate that this object was a “planet,” as they had been looking for it and thought it was massive enough to account for Uranus’ orbit.
The Second Planet X
However, there were still some unexplained perturbations of Uranus’ orbit. These persisted for 70 years, to the time that Percival Lowell became interested in the problem and wanted to search for a now possible ninth planet at his observatory in New Mexico. I think that he was the one who really first coined the term, “Planet X.” Lowell searched for 12 years, 1905-1916, until he died, without finding it.
The search resumed in 1929 when the then-director of the observatory ass read more...