The scientists agreed that for a celestial body to qualify as a planet:
- it must be in orbit around the Sun
- it must be large enough that it takes on a nearly round shape
- it has cleared its orbit of other objects
Pluto was automatically disqualified because its highly elliptical orbit overlaps with that of Neptune. It will now join a new category of dwarf planets.
Pluto is no longer a planet because of it overlapping Neptunes orbit.