Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Giant planet
open-in-new
<p>A giant planet, sometimes referred to as a jovian planet (<i>Jove</i> being another name for the Roman god <a href="/facts/Jupiter_(mythology)/JPetM2m9">Jupiter</a>), is a diverse type of <a href="/facts/Planet/rbPjE6Bx">planet</a> much larger than Earth. Giant planets are usually primarily composed of low-<a href="/facts/Boiling_point/E2BK9QoS">boiling point</a> materials (<a href="/facts/Volatile_(astrogeology)/yYCe49qX">volatiles</a>), rather than <a href="/facts/Rock_(geology)/FXCJkmop">rock</a> or other <a href="/facts/Solid/hj5UsXno">solid</a> matter, but <a href="/facts/Massive_solid_planet/RpGsQceL">massive solid planets</a> can also exist. There are four such planets in the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>: <a href="/facts/Jupiter/95m7XjMT">Jupiter</a>, <a href="/facts/Saturn/D54LcGJ9">Saturn</a>, <a href="/facts/Uranus/x7YwT1ar">Uranus</a>, and <a href="/facts/Neptune/1eucwHIC">Neptune</a>. Many <a href="/facts/Exoplanet/zjfmqfUf">extrasolar</a> giant planets have been identified. </p><p>Giant planets are sometimes known as <a href="/facts/Gas_giant/pmF6KztG">gas giants</a>, but many astronomers now apply the term only to Jupiter and Saturn, classifying Uranus and Neptune, which have different compositions, as <a href="/facts/Ice_giant/mJ4YTuup">ice giants</a>. Both names are potentially misleading; the Solar System's giant planets all consist primarily of fluids above their <a href="/facts/Critical_point_(thermodynamics)/pkM7RLJK">critical points</a>, where distinct gas and liquid phases do not exist. Jupiter and Saturn are principally made of <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a> and <a href="/facts/Helium/yRul93TG">helium</a>, whilst Uranus and Neptune consist of water, <a href="/facts/Ammonia/MtLtJFtz">ammonia</a>, and <a href="/facts/Methane/kBHneYnh">methane</a>. </p><p>The defining differences between a <a href="/facts/Brown_dwarf/fa7kr9lH">very low-mass brown dwarf</a> and a massive gas giant (~13 <a href="/facts/Jupiter_mass/EtLUmeEN">MJ</a>) are debated. One school of thought is based on planetary formation; the other, on the physics of the interior of planets. Part of the debate concerns whether brown dwarfs must, by definition, have experienced <a href="/facts/Nuclear_fusion/hP0gLDqj">nuclear fusion</a> at some point in their history. </p>