How do gas planets stay together?
Question
Why do gas planets like Neptune and Saturn exist? What keeps the gas together and doesn’t just disappear into space?Malcolm, M25
Answer
** Definitive **Name: Hal, Brighton
Qualification: Science Professor and Mystery Hour legend
Answer: There are two answers. Firstly, you can apply the same logic to the Earth – why doesn’t the air around the Earth dissipate, seeing nothing it holding it in. The answer is that gases are affected by gravity the same as everything else and is pulled downwards. The second answer is that the normal rules don’t apply in space, as gravity is so different. On Jupiter and Saturn, you’ve got helium and hydrogen under immense pressure and what would usually be a gas in our atmosphere, are squashed together so much, they become a strange liquid. In the case of Jupiter, you’ve got metallic hydrogen gas, which conducts electricity – something that could never happen on Earth.