Originally Posted by proplyd

It has been a while since anyone posted here. It has been since before the International Astronomy Union demoted Pluto to a dwarf planet. If this one goes though, it will be my first.

They unintentionally demoted another planet when they got Pluto, the smallest of the traditional nine planets. They also demoted Jupiter, the largest of them.

The new definition of a planet requires that it orbit the Sun. Jupiter does not, technically. The center of mass between Jupiter and the Sun, their barycenter, lies a whisker outside the surface of the Sun. Technically, Jupiter and the Sun orbit each other. Jupiter does not orbit the Sun, and therefore is not a planet.