Is there a reason why we have four “rock” planets lined up followed by four “gas” planets in a row, or is it merely coincidence?

Question

Is there a reason why we have four “rock” planets lined up followed by four “gas” planets in a row, or is it merely coincidence?

In: Planetary Science

Answer 1

Yes. It’s called the “frost line” and it is the distance from the sun beyond which it is cold enough for gases like hydrogen, helium, methane, etc. will condense and form thick atmospheres like you find in the gas giants.