The scientific paper "A Geophysical Planet Definition” published by Planetary and Lunar Science, has brought the categorization of the moon, Pluto, and a few other bodies in space into question. Part of the team responsible for this study is Alan Stern.
Stern was part of NASA’s New Horizons mission that flew by Pluto back in July of 2015. The argument in favor of reclassification rests on the theory that the geophysics of a body should determine whether or not is labeled as a plant. As of now, a orbit around our Sun is what makes a planet.
Justice for Pluto
Back in 2006, scientists demoted Pluto to a “trans-Uranian dwarf planet” against popular opinion. Stern's mission with the New Horizons mission was to fly by Pluto. He was furious when the decision for demotion was passed down. The rest of the world mourned the loss of Pluto as well.
Many people still have a difficult time coping with just 8 planets in the Solar System after having used "My Very Energetic Mother Just Served Us Nine Pies" or some other version of a mnemonic device (memory aid). After much news this week in the world of astronomy, the moon may be reclassified, and Pluto may become a planet again.
The History of the Moon
This is not the first time that people have thought that the moon is a planet.
Greek and medieval European astronomers believed that it was already a planet. Astronomers took a special interest the study of the moon. They discovered "tidal locking" which is when a body in space always faces in the same direction. Aristotle came in with a different theory. He was able to show that the moon could not move of rotate.
He argued that it looks like it's moving when really it is simply being carried by Earth.
Other scientists counter with the notion that moons should be closer to their planet, while the moon is not as close to Earth as some of the other planets' moons. In 1543, Copernicus published Heliocentric Astronomy which demoted the moon from its former planetary status. As of now, no decision has been made about the reclassification of the moon nor Pluto.
