system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can’t a planet the size of Jupiter be rocky like Earth? Side question: if it was possible to be rocky could Jupiter break from the Sun’s orbit?
gpt
They can be, at least there isn’t like a LAW making it so they can’t exist.

The biggest we’ve found though is a massive planet around another star 40 times the size of earth by material. So 40 times by mass

Jupiter on the other hand is about 318 times as massive,

A the thing that is possible limiting giant rocky planets from existing is just the need for material.

Jupiter is only so massive because it’s made up of A LOT of gas, Jupiter is 90% hydrogen, the most abundant element there is.

Compared to hydrogen, there is just significantly less material of the larger elements that make up rocks, your carbons, silicons, irons, oxygens, and others.

For if it could break free from the solar system, if you replaced jupiter with the same MASS of rock, then gravitationally nothing would change and it’s orbit wouldn’t change.

If you replaced it with the same VOLUME of rock, it would be significantly more massive (since gas is less dense than rock) which would possibly cause some weird gravitational problems.