Question: Why is jupeter a planet when it is nothing but gass

Hayley Evers-King answered on 20 Mar 2013:

The word planet originally meant “wandering star” in ancient greek and we know stars can be made of gas, so maybe its not surprising that gas planets exist. The more modern definition makes a planet is something that is massive enough to become rounded by its own gravity, but not massive enough to have thermonuclear fusion (stars do). So Jupiter, because it’s big enough to become this round collection of gas – is a planet, just like the other gas giants.