Gas giant

A large planet composed mainly of hydrogen and helium, with a deep atmosphere and no well-defined solid surface. Its interior becomes increasingly dense under extreme pressure.

Hydrogen: The lightest chemical element, abundant in stars and giant planets. It is the dominant element in a gas giant’s atmosphere and interior.
Hydrostatic equilibrium: A state in which inward gravity is balanced by outward pressure within a body. It governs the balance between gravity and pressure throughout a gas giant.
Jupiter: The largest planet in the Solar System, a hydrogen- and helium-rich world with dozens of moons. It is the Solar System’s largest example, with a deep atmosphere and likely metallic-hydrogen interior.
Core accretion: A planet-formation model in which solid material builds a core that later attracts surrounding gas. It explains how a growing core can capture a massive hydrogen-helium envelope.
Exoplanet: A planet that orbits a star other than the Sun. Gas giants around other stars show how common and varied giant planets can be.
Helium: A light, chemically inert element that is the second most abundant element in the universe. It is the second major ingredient of gas giant interiors.
Adiabatic process: A thermodynamic change that occurs without heat entering or leaving a system. Rising and sinking gas often changes temperature approximately adiabatically.
Saturn: The Solar System’s second-largest planet, known for its extensive rings and low average density. Its low density and prominent rings make it a contrasting case to Jupiter.
Disk instability: A planet-formation model in which parts of a protoplanetary disk collapse directly under gravity. It offers an alternative route to giant-planet formation without first building a large solid core.
Hot Jupiter: A gas giant on a close, short-period orbit around its star. These unusually warm, close-in giants challenge simple accounts of where planets form.

Linked from 11 pages