Why are large, spherical bodies like Ganymede or Titan typically excluded from planet classification despite their size?

Answer

They orbit another planet rather than orbiting the Sun directly.

A fundamental constraint of the current IAU framework is that the body must orbit the Sun directly; moons orbit other planets and are therefore excluded regardless of their shape or relative size.

Why are large, spherical bodies like Ganymede or Titan typically excluded from planet classification despite their size?

#Videos

Clearing the neighbourhood - YouTube

DefinitionastronomyorbitplanetIAUclearing the neighborhood