Tama Graham, of Pt Chalmers School, asks :-

The composite standard 2 - form 2 class at Rangwahia School, asked:- Pippa Childs, aged 10 of Cashmere Primary School, asked:-

What is inside Jupiter?

Neil Ashcroft, a condensed matter physicist at Cornell University, USA, responded.

Jupiter is very large, about 11 times bigger than the Earth, and over 300 times more massive. But the stuff it contains is very different; over 9 atoms out of 10 in Jupiter are hydrogen atoms, the lightest of all atoms. Under ordinary conditions we think of hydrogen as a gas. If we cool hydrogen gas enough it forms an electrically insulating liquid, and if we cool it even more, it forms a solid (just like the progression of steam to water to ice). Inside Jupiter the hydrogen is under enormous pressures because of the gravitational forces in such a large planet.

One observation that must be explained is that Jupiter has a whopping magnetic field, very much larger than one we have on our own earth. Many years ago it was predicted that under very high pressures hydrogen has the electrons ripped off it and so can become a conductor of electricity. Electrical currents in the interior can then produce the observed magnetic field of Jupiter.

An exciting developement was made earlier this year by physicists at Lawrence Livermore National Laboratory in California. With shock-waves they managed to duplicate in hydrogen not only the pressure in parts of Jupiter, but also the temperature. And, they managed also to measure the conductivity of hydrogen; it was indeed in the range of certain liquid metals!

The most abundant element in our entire planetary system is hydrogen. It now appears that more than half of it is in a metal form!