Editing Giant planet (section)

==Subtypes==

===Gas giants===
{{Main article|Gas giant}}
[[File:Saturn north polar vortex 2012-11-27.jpg|thumb|right|Saturn's north polar vortex]]
Gas giants consist mostly of hydrogen and helium. The Solar System's gas giants, [[Jupiter]] and [[Saturn]], have heavier elements making up between 3 and 13 percent of their mass.<ref name="Guillot">The Interior of Jupiter, Guillot et al., in ''Jupiter: The Planet, Satellites and Magnetosphere'', Bagenal et al., editors, Cambridge University Press, 2004</ref> Gas giants are thought to consist of an outer layer of [[molecular hydrogen]], surrounding a layer of liquid [[metallic hydrogen]], with a probable molten core with a rocky composition.

Jupiter and Saturn's outermost portion of the hydrogen atmosphere has many layers of visible clouds that are mostly composed of water and ammonia. The layer of metallic hydrogen makes up the bulk of each planet, and is referred to as "metallic" because the very high pressure turns hydrogen into an electrical conductor. The core is thought to consist of heavier elements at such high temperatures (20,000 K) and pressures that their properties are poorly understood.<ref name="Guillot"/>

===Ice giants===
{{Main article|Ice giant}}
[[File:Hubble's Decade-Long Views of the Outer Solar System Planets (2024-010).png|thumb|Composite image of Hubble photos showing four giant planets of the Solar System, tracking seasonal changes during ten years of observations (2014-2024)]]
Ice giants have distinctly different interior compositions from gas giants. The Solar System's ice giants, [[Uranus]] and [[Neptune]], have a hydrogen-rich atmosphere that extends from the cloud tops down to about 80% (Uranus) or 85% (Neptune) of their radius. Below this, they are predominantly "icy", i.e. consisting mostly of water, methane, and ammonia. There is also some rock and gas, but various proportions of ice–rock–gas could mimic pure ice, so that the exact proportions are unknown.<ref name="mcfadden2007"/>

Uranus and Neptune have very hazy atmospheric layers with small amounts of methane, giving them light aquamarine colors. Both have magnetic fields that are sharply inclined to their axes of rotation.

Unlike the other giant planets, Uranus has an extreme tilt that causes its seasons to be severely pronounced. The two planets also have other subtle but important differences. Uranus has more hydrogen and helium than Neptune despite being less massive overall. Neptune is therefore denser and has much more internal heat and a more active atmosphere. The [[Nice model]], in fact, suggests that Neptune formed closer to the [[Sun]] than Uranus did, and should therefore have more heavy elements.

===Massive solid planets===

[[Massive solid planets]] seemingly can also exist, though their formation mechanisms and occurrence remain subjects of ongoing research and debate.

The possibility of solid planets up to thousands of Earth masses forming around massive stars ([[B-type main-sequence star|B-type]] and [[O-type main-sequence star|O-type]] stars; 5–120 solar masses) has been suggested in some earlier studies.<ref name="seager2007"/> The hypothesis proposed that the [[protoplanetary disk]] around such stars would contain enough heavy elements, and that high [[UV radiation]] and strong [[stellar wind|winds]] could [[Photoevaporation|photoevaporate]] the gas in the disk, leaving just the heavy elements. For comparison, Neptune's mass equals 17 Earth masses, Jupiter has 318 Earth masses, and the 13 Jupiter-mass limit used in the [[IAU]]'s working definition of an exoplanet equals approximately 4000 Earth masses.<ref name="seager2007"/>

However, it is important to note that more recent research has called into question the likelihood of massive solid planet formation around very massive stars (https://arxiv.org/pdf/1103.0556). Studies have shown that the ratio of protoplanetary disk mass to stellar mass decreases rapidly for stars above 10 solar masses, falling to less than 10^-4.  Furthermore, no protoplanetary disks have been observed around O-type stars to date.

The original suggestion of massive solid planets forming around 5-120 solar mass stars, presented in earlier literature, lacks substantial supporting evidence or citations to planetary formation theories.<ref name="seager2007"/> The study in question primarily focused on simulating mass-radius relationships for rocky planets, including hypothetical super-massive solid planets, but did not investigate whether planetary formation theories actually support the existence of such objects. The authors of that study acknowledged that "Such massive exoplanets are not yet known to exist."<ref name="seager2007"/>

Given these considerations, the formation and existence of massive solid planets around very massive stars remain speculative and require further research and observational evidence.

===Super-Puffs===
{{main|Super-puff}}

A super-puff is a type of [[exoplanet]] with a [[mass]] only a few times larger than
[[Earth]]’s but a radius larger than [[Neptune]], giving it a very low mean [[density]]. They are cooler and less massive than the [[Puffy planet|inflated low-density hot-Jupiters]]. The most extreme examples known are the three planets around [[Kepler-51]] which are all [[Jupiter]]-sized but with densities below 0.1 g/cm<sup>3</sup>.<ref name="libby-roberts2020"/>