icegiant

An ice giant is a class of large planets whose interiors contain a substantial proportion of volatile compounds such as water, ammonia, and methane in the form of dense ices. Ice giants differ from gas giants, which are dominated by hydrogen and helium, and from terrestrial planets which have little to no significant ice or hydrogen/helium envelopes.

In typical models, an ice giant consists of a rocky/metallic core surrounded by a thick mantle of high-pressure ices, overlayed by a relatively thin or modest hydrogen–helium atmosphere. The overall composition is enriched in volatiles relative to gas giants, and the planets have masses roughly in the range of about 10 to 15 Earth masses (some sources cite up to around 20) and radii about 3.5 to 4 Earth radii, giving densities around 1.3 to 1.7 g/cm3.

Formation and location: Ice giants are thought to form beyond the snow line where water and other volatiles can condense, later accreting icy material and gas. They typically orbit farther from their stars than rocky planets and often have multiple moons and, in some cases, ring systems. Their atmospheres can show winds and weather patterns; methane absorption gives them blue to blue-green hues, as seen in Uranus and Neptune.

Examples: In our solar system, Uranus and Neptune are the archetypal ice giants. In exoplanet research, the term is used to describe Neptune-like or larger planets with substantial volatile-rich interiors, distinct from gas giants and from smaller rocky worlds.