When was Neptune discovered?
Q: When was Neptune discovered?
A: Neptune was discovered in 1846.
Q: Why did people think there might be more planets beyond Neptune?
A: After the discovery of Neptune, people thought there might be more planets further away from the sun than Neptune.
Q: Who stated that there must be another planet-like body beyond Neptune?
A: Percival Lowell stated that there must be another planet-like body farther out than Neptune.
Q: What did Lowell say a planet-like object beyond Neptune could explain?
A: Lowell said that such a planet-like object could explain some irregularities in the orbits of the gas giants, in particular Uranus and Neptune.
Q: What did Lowell call the hypothetical ninth planet beyond Neptune?
A: Lowell called the hypothetical ninth planet beyond Neptune "Planet X".
Q: What effect could the gravity of a large unseen ninth planet have on Uranus?
A: The gravity of a large unseen ninth planet could have perturbed Uranus enough to explain the irregularities in its orbit.
Q: When did Percival Lowell make his hypothesis about a ninth planet?
A: Percival Lowell made his hypothesis about a ninth planet in the early 20th century.
