A large planet composed primarily of hydrogen and helium with a relatively small rocky core, characterized by thick atmospheres and low overall density. Jupiter and Saturn are the gas giants in our solar system.
The term emerged in the mid-20th century as astronomers distinguished between rocky terrestrial planets and the large, low-density outer planets. 'Gas' refers to their dominant atmospheric composition, while 'giant' describes their enormous size compared to terrestrial planets.
Gas giants are cosmic vacuum cleaners that protect inner planets from asteroid and comet impacts - Jupiter has been called Earth's guardian angel! Their powerful gravity fields capture or deflect potentially dangerous objects, which may have been crucial for allowing complex life to evolve on Earth.
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