Glossary term: Giant Planet

Description: A giant planet is a large body mostly composed of hydrogen, helium, or more complex molecules such as water, methane or ammonia. While a terrestrial planet is mostly composed of material with a very high boiling point such as iron or rock, giant planets are thought to have a solid core surrounded by other material. Giant planets fall into two categories: gas giants which are mostly made up of hydrogen and helium, and ice giants which are mostly made up of water, methane, and ammonia surrounded by an atmosphere of hydrogen and helium. The four largest planets in the Solar System (Jupiter, Saturn, Neptune, and Uranus) are all giant planets.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

Related Media

The planet Jupiter with horizontal cloud ribbons and the great red spot


Caption: This full disk view of Jupiter was obtained on 21 April 2014 with Hubble's Wide Field Camera 3 (WFC3). It shows the prominent great red spot, a gigantic cyclone. Cloud ribbons cover the surface, whose colours stem from gases like ammonia and other chemical compounds.
Credit: NASA, ESA, and A. Simon (Goddard Space Flight Center) credit link
License: CC-BY-4.0 Creative Comments Attribution 4.0 International (CC BY 4.0) icons
The planet Saturn with pale brownish cloud ribbons and its thin and extended greyish rings


Caption: The NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 observed Saturn on 20 June 2019 as the planet made its closest approach to Earth this year, at approximately 1.36 billion kilometres away. The image shows coloured bands of gas on the planet's surface as well as its prominent rings made of ice and rocky material.
Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley) credit link
License: CC-BY-4.0 Creative Comments Attribution 4.0 International (CC BY 4.0) icons
Uranus showing a uniformly greenish-blue coloured appearance

Uranus in natural colours

Caption: This is an image of the planet Uranus taken by the spacecraft Voyager 2 in 1986. Its appearance is close to what the naked eye would see. The greenish-blue colour indicates an atmosphere containing methane.
Credit: NASA/JPL-Caltech credit link
License: PD Public Domain icons
Uranus appears as a light blue disk with and a pale polar region. Thin white rings surround the planet

Uranus with rings

Caption: The NASA/ESA Hubble Space Telescope’s ACS/HRC camera observed Uranus in August 2005. The surface depicts white clouds and a bright polar region. The rings around Uranus are narrow and contain rocky material from tiny dust particles up to metre-sized boulders.
Credit: NASA, ESA, and M. Showalter (SETI Institute) credit link
License: PD Public Domain icons
Neptune is spherical and blue with thin bands of white cloud and a slightly darker spot just below its equator


Caption: Voyager 2 Narrow Angle Camera image of Neptune taken in August 1989. The Great Dark Spot, flanked by cirrus clouds, is at center. A smaller dark storm, Dark Spot Jr., is rotating into view at bottom left. Additionally, a patch of white cirrus clouds to its north, named "Scooter" for its rapid motion relative to other features, is visible.
Credit: NASA / JPL / Voyager-ISS / Justin Cowart credit link
License: PD Public Domain icons