Short answers, pulled from the story.
The oldest surviving planetary astronomical text is the Venus tablet of Ammisaduqa, which dates back to the 7th century BC but likely preserves observations from the second millennium BC.
The International Astronomical Union established a three-part definition of a planet in August 2006, which reclassified Pluto, Ceres, and Eris as dwarf planets and reduced the count of major planets to eight.
Only Venus and Mars lack a global magnetic field because they do not have the internal flows of electrically conducting material required to generate a geodynamo.
The planet Uranus was discovered in 1781 by William Herschel, which shattered the ancient count of seven planets and proved the solar system extended beyond the reach of the naked eye.
The nebular hypothesis posits that planets coalesce during the collapse of an interstellar cloud into a thin disk of gas and dust surrounding a young protostar, where dust particles stick together through accretion to form planetesimals and eventually protoplanets.
Earth was discovered as a planet only in the 17th century and kept its Old English name derived from the word for ground and dirt.