Giant planet landing on a giant planet may or may not be possible, depending on the size and composition of its core. Gas giants consist mostly of hydrogen and helium. The Solar System's gas giants, Jupiter and Saturn, have heavier elements making up between 3 and 13 percent of their mass. Gas giants are thought to consist of an outer layer of molecular hydrogen, surrounding a layer of liquid metallic hydrogen, with a probable molten core with a rocky composition. Jupiter and Saturn's outermost portion of the hydrogen atmosphere has many layers of visible clouds that are mostly composed of water and
Red-giant branch terminology is still frequently used today. Modern stellar physics has modelled the internal processes that produce the different phases of the post-main-sequence life of moderate-mass stars, with ever-increasingly complexity and precision. The results of RGB research are themselves being used as the basis for research in other areas. When a star with a mass from about (solar mass) to ( for low-metallicity stars) exhausts its core hydrogen, it enters a phase of hydrogen shell burning during which it becomes a red giant, larger and cooler than on the main sequence. During hydrogen shell burning, the interior of the star goes