Ice giant

In Astronomy the term ice giant refers to the very large planets, like Planet Uranus and Planet Neptune that are smaller than gas giants, like Planet Saturn and Planet Jupiter.^[1] While both kinds of planets are largely composed of gas, the more massive gas Giants have a higher proportion of Hydrogen and Helium. Ice Giants have a relatively higher proportion of water, methane, Carbon Dioxide -- compounds that Astronomers classify as ices.

In recent decades Astronomers believe they have found thousands of exoplanets, planets orbiting distant stars. Among those exoplanet they have found planets the mass of Uranus and Neptune, that are located much closer to their primary stars. They are currently discussing how much these "Hot-Neptunes" differ from the Solar system's cold ice Giants.

Other stellar systems also seem to contain classes of planets smaller than the Solar system's ice Giants, but larger than Planet Earth. They have tentatively called these sub-Neptunes and super-Earths.

References

↑ "Not a Heart of Ice". The Planetary Society. 2019-04-02. Archived from the original on 2020-08-08. Retrieved 2026-07-31. This is how the giant planets got sub-divided into two different flavors of “giant.” Jupiter and Saturn, which had to be mostly hydrogen and helium, became known as the “gas giants,” while the smaller, less massive planets, which nevertheless had to be composed mostly of compounds that would have been in the form of ice in the outer solar nebula, became the “ice giants.”

[planetary-2019-04-02-1] "Not a Heart of Ice". The Planetary Society. 2019-04-02. Archived from the original on 2020-08-08. Retrieved 2026-07-31. This is how the giant planets got sub-divided into two different flavors of “giant.” Jupiter and Saturn, which had to be mostly hydrogen and helium, became known as the “gas giants,” while the smaller, less massive planets, which nevertheless had to be composed mostly of compounds that would have been in the form of ice in the outer solar nebula, became the “ice giants.”

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