ElI5: how do they know what other planets are made off, how can the be so sure? Jupiter could be made of a completely unknown gas?

Question

ElI5: how do they know what other planets are made off, how can the be so sure? Jupiter could be made of a completely unknown gas?

In: 96

Answer 1

Guesswork, mostly. We look at the gravity, the apparent size, what kind of color it is, and how much heat it gives off in infrared. Then we make a mathematical model to try to explain all that.

We don’t actually know what Jupiter is made of. We just have some reasonable guesses that match our observations.