gas giant

American  

[gas jahy-uhnt] / ˈgæs ˌdʒaɪ ənt /

noun

Astronomy.

1. a giant planet composed mostly of hydrogen and helium: the two gas giants in our solar system, Jupiter and Saturn, are sometimes called failed stars because their composition is similar to that of stars, but this is largely considered misleading, as gas giants, unlike brown dwarfs, do not form as stars do.

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gas giant British  

noun

1. one of the four planets in our solar system that are composed chiefly of hydrogen and helium, namely Jupiter, Saturn, Uranus, and Neptune

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gas giant Scientific  

1. A large, massive, low-density planet composed primarily of hydrogen, helium, methane, and ammonia in either gaseous or liquid state. Gas giants have swirling atmospheres primarily of hydrogen and helium, with no well-defined planetary surface; they are assumed to have rocky cores. They are also characterized by ring systems, although only Saturn's is readily visible from Earth. Our solar system contains four gas giants: Jupiter, Saturn, Uranus, and Neptune. The majority of extrasolar planets discovered so far are the size of the solar system's gas giants, although they orbit their stars much more closely and may differ in composition from ours.

2. Also called Jovian planet

3. Compare terrestrial planet

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Etymology

Origin of gas giant

First recorded in 1950–55

Example Sentences

There, a gas giant about 7 times the mass of Jupiter rotates six times faster than a brown dwarf companion that is roughly 24 times Jupiter's mass.

From Science Daily • Jun. 13, 2026

He may have been referring to the Power of Siberia 2 pipeline, for which Russian gas giant Gazprom and the China National Petroleum Corporation reportedly signed a preliminary deal following years of stalled negotiations.

From BBC • May 18, 2026

BP said it was halting stock buybacks as the oil and gas giant said it wanted to rebuild its balance sheet.

From MarketWatch • Feb. 10, 2026

He also called for the quick appointment of a new head of Ukrhydroenergo, a hydropower generating company, and reforms for oil and gas giant Naftogaz and the nation's Gas Transmission System Operator.

From BBC • Nov. 15, 2025

I’m like that theoretical brown dwarf star or gas giant planet lurking at the far edges of our solar system, way beyond Pluto.

From "Shine!" by J.J. and Chris Grabenstein