Definition
A gas giant planet is a type of planet with large mass and composition dominated by light gases, mainly hydrogen and helium. Unlike terrestrial planets, it lacks a defined solid surface. Its appearance often shows atmospheric bands, persistent storms, and complex cloud layers.
Internal structure
The internal structure includes a thick outer gas layer transitioning into compressed gases, then into liquid or metallic states under high pressure. At the center may lie a dense core, possibly rocky or icy, depending on the model. Transitions between layers are continuous.
Atmosphere and dynamics
The atmosphere consists of light gases with traces of ammonia, methane, water vapor, and other volatiles. It is stirred by high-speed winds, vortex systems, and differential circulation. The structure includes cloud bands parallel to the equator, shaped by the planet s rapid rotation.
Formation and evolution
Gas giant planets form in the outer regions of protoplanetary disks, where gases and ices accumulate around an initial core. This leads to rapid growth through accretion. Their evolution depends on heat loss, gravitational contraction, and interactions with other objects or the remaining disk.
Types and variants
Various types of gas giants exist based on temperature, composition, and location. Some, called cold giants, contain many ices and gases, while others close to their star display distinct atmospheric traits due to intense radiation. Subcategories like hot giants or subnebulae can be identified by observable characteristics.