PX282 - K2b - interiors of ice giants

• the masses of uranus and neptune are dominated by 'ices' in fluid form. eg: H${}_2$O, NH${}_3$, CH${}_4$, CO${}_2$, CO
• majority of the volume is H and He
• this is why they have intermediate densities, sitting between the terrestrials and the gas giants
• they are supported by large over-abundance of CH${}_4$ in atmospheres

image: Carroll & Ostile, An Introduction to Modern Astrophysics (2007)

• they are rapid rotators, but lower mass allows spin obliquity to be perturbed as they do not have as much spin angular momenta

• uranus has an obliquity of $97.8\mathrm{°}$, which is likely due to a giant collision

• their magnetic moments are $\sim \times 50$ and $\times 25$ of earth's, respectively

• this is despite a lack of metallic hydrogen

• this is because the ices become ionized at extreme pressures

• they have complex corkscrew magnetospheres due to high obliquities, and dipole misalignments with the spin axes