The definition approved by the International Astronomical Union (IAU) in 2006, demoted Pluto to “non-planet,” dropping the number of planets in our solar system from nine to eight. This definition differs from the three-element IAU definition in that it makes no reference to the celestial body’s surroundings. Otherwise, Pluto fit the IAU definition: it orbits the Sun and it is massive enough that the forces of gravity have made it round. Researchers have argued in the past that the IAU definition also excludes Earth, Mars, Jupiter and Neptune, which share their orbits with asteroids. The new geophysical definition omits stars, black holes, asteroids and meteorites, but includes everything else in our solar system.

Source: Mint March 19, 2017 10:30 UTC