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Incoming links: Neptune Facts by National Aeronautics and Space Administration
Neptune Created 2026-10-06 Updated 2026-11-05
Neptune is an ice giant in the outer Solar system. It has a hydrogen-helium-rich outer atmosphere containing methane, while a substantial fraction of its interior is material heavier than those two light elements. In the classification name, ice refers to volatile-rich constituents rather than proving that the deep interior is a rigid block of frozen material.[ref]
Neptune Facts by National Aeronautics and Space Administration. Structure and atmosphere: ice-giant composition and methane-bearing outer layers
Its appearance illustrates how selective molecular absorption changes reflected colour. Interior models must instead satisfy hydrostatic equilibrium and an equation of state under high pressure. Hot Neptunes are named by an approximate size or mass comparison; that name does not establish that they share Neptune's present thermal state or composition.