On August 24, 2006, the International Astronomical Union redefined the term “planet” and decided on the following conditions:

  1. A planet orbits around a star and is neither a star nor a moon.
  2. Its shape is spherical due to its gravity.
  3. It has “cleared” the space of its orbit.

A “dwarf planet” such as Pluto only meets the first two conditions. Consequently, kids today are learning that our solar system only has 8 planets.

Celestial bodies that only meet the fist condition are referred to as small solar system bodies, for example, asteroids or comets.