ABSTRACT
Hydrogen is the major constituent in astronomical objects such as stars and giant planets. Stellar and planetary magnetism may thus be strongly influenced by the states and phase transformations in hydrogen matter such as metallization and magnetization. The hydrogen densities required for magnetization may be expected in an outer shell of a hydrogen-rich white dwarf at some 70%–90% of the stellar radius, where the mass densities may take on values lower by three or more orders of magnitude than those in the core. The first-order metal-insulator (MI) transitions in hydrogen may predict the existence of a boundary layer inside Jupiter across which the mass density and the resistivity change discontinuously. The first-order MI transitions in dense hydrogen may be looked upon as an element of physics that is essential to the Jovian magnetic activities. Highly conductive liquid-metallic hydrogen in motion is capable of distorting and amplifying the magnetic field configurations of stars and planets.
