NASA's The Space PlaceSince its discovery in 1930, Pluto was heralded as the ninth planet in our Solar System. Last year, a team of scientists put forth a new definition of planet that would bring Pluto back into the fold, and this definition has been endorsed by Alan Stern and David Grinspoon, authors of a new book on the New Horizons mission and "the planet" Pluto. A planet had to orbit the Sun and no other object: Earth could be a planet but not the Moon. NASA/JHUAPL/SwRIAnd yet, that's the other hand: you have to ignore all of astronomy to consider Pluto a planet. That's the question you need to ask yourself: should an object's position in its Solar System determine what a planet is?

Source: Forbes May 08, 2018 13:52 UTC