If the definition of a planet is something like the body must clear the path of orbit of debris, how is Jupiter a planet, considering it has like 63 moons and rings? What about Saturn with its moons and its rings?

Question

I’m aware that Neptune and Uranus also have rings, but shouldn’t those disqualify them being labelled planets? Or any celestial body with a satellite?

In: Physics

Answer 1

The idea of “clearing one’s orbit” is obviously open to interpretation, as in all honesty no planet’s orbit is completely clear (even Earth’s). Further, satellites of the planets are considered to be a “part” of that planet (from a gravitational perspective) in this context, as the relationship between those planets and their satellites is much more significant than between those satellites and *other* objects (e.g. the Sun).

The point of the “cleared orbit” was more to showcase that the 8 planets **overwhelmingly** dominate the distribution of mass in their specific orbits. Pluto does not; it’s just one iceball among many. Further, the reason Jupiter’s orbit is not cleared (e.g. the Trojan asteroids) is entirely *because* of how massive it is.

More to the point, the definition of planet was driving primarily by the need to demarcate a difference between the classical planets and the plethora of smaller objects that exist in the asteroid belt and beyond the orbit of Neptune, some of which are larger than Pluto.