View source for Giant planet

{{short description|Planet much larger than the Earth}}
{{Multiple image
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|image1=Jupiter OPAL 2024 (cropped).png{{!}}Jupiter
|image2=Saturn_during_Equinox_(rot45).jpg{{!}}Saturn
|image3=Uranus Voyager2 color calibrated.png{{!}}Uranus
|image4=Neptune Voyager2 color calibrated.png{{!}}Neptune
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The four giant planets of the Solar System:
* (''top'') [[Jupiter]] and [[Saturn]] ([[gas giant]]s)
* (''bottom'') [[Uranus]] and [[Neptune]] ([[ice giant]]s)
''Shown in order from the [[Sun]] and in [[False color#True color|true color]]. Sizes are not to scale.''
}}

A '''giant planet''' is a diverse type of [[planet]] much larger than Earth. It is sometimes referred to as a '''jovian planet''', with ''Jove'' being another name for the Roman god [[Jupiter (mythology)|Jupiter]]. Giant planets are usually primarily composed of low-[[boiling point]] materials ([[volatile (astrogeology)|volatiles]]), rather than [[rock (geology)|rock]] or other [[solid]] matter, but [[mega-Earth]]s do also exist. There are four such giant planets in the [[Solar System]]: [[Jupiter]], [[Saturn]], [[Uranus]], and [[Neptune]]. Many [[exoplanet|extrasolar]] giant planets have been identified.

Giant planets are sometimes known as [[gas giant]]s, but many astronomers now apply the term only to Jupiter and Saturn, classifying Uranus and Neptune, which have different compositions, as [[ice giant]]s. Both names are potentially misleading; the Solar System's giant planets all consist primarily of fluids above their [[critical point (thermodynamics)|critical points]], where distinct gas and liquid phases do not exist. Jupiter and Saturn are principally made of [[hydrogen]] and [[helium]], whilst Uranus and Neptune consist of water, [[ammonia]], and [[methane]].

The defining differences between a [[Brown dwarf#Low-mass brown dwarfs versus high-mass planets|very low-mass brown dwarf]] and a massive gas giant ({{Jupiter mass|~13|link=yes}}) 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 [[nuclear fusion]] at some point in their history.<ref name="PT-June2008" />

== Terminology ==
The term ''gas giant'' was coined in 1952 by science fiction writer [[James Blish]] and was originally used to refer to all giant planets. Arguably it is something of a misnomer, because throughout most of the volume of these planets the pressure is so high that matter is not in gaseous form.<ref name="d'angelo2011"/> Other than the upper layers of the atmosphere,<ref name="d'angelo2021"/> all matter is likely beyond the [[critical point (thermodynamics)#Liquid–vapor critical point|critical point]], where there is no distinction between liquids and gases. ''Fluid planet'' would be a more accurate term. Jupiter also has [[metallic hydrogen]] near its center, but much of its volume is hydrogen, helium, and traces of other gases above their critical points. The observable atmospheres of all these planets (at less than a unit [[optical depth]]) are quite thin compared to their radii, only extending perhaps one percent of the way to the center. Thus, the observable parts are gaseous (in contrast to [[Mars]] and Earth, which have gaseous atmospheres through which the crust can be seen).

The rather misleading term has caught on because planetary scientists typically use ''rock'', ''gas'', and ''ice'' as shorthands for classes of elements and compounds commonly found as planetary constituents, irrespective of the matter's [[phase of matter|phase]]. In the outer Solar System, hydrogen and helium are referred to as ''gas''; water, methane, and ammonia as ''ice''; and silicates and metals as ''rock''. When deep planetary interiors are considered, it may not be far off to say that, by ''ice'' astronomers mean [[oxygen]] and [[carbon]], by ''rock'' they mean [[silicon]], and by ''gas'' they mean hydrogen and helium. The many ways in which Uranus and Neptune differ from Jupiter and Saturn have led some to use the term only for planets similar to the latter two. With this terminology in mind, some astronomers have started referring to Uranus and Neptune as [[ice giant]]s to indicate the predominance of the ''ices'' (in fluid form) in their interior composition.<ref name="NASAames2006"/>

The alternative term ''jovian planet'' refers to the Roman god [[Jupiter (mythology)|Jupiter]]—the genitive form of which is ''Jovis'', hence ''Jovian''—and was intended to indicate that all of these planets were similar to Jupiter.

Objects large enough to start [[deuterium]] [[Nuclear fusion|fusion]] (above 13 [[Jupiter mass]]es for solar composition) are called [[brown dwarf]]s, and these occupy the mass range between that of large giant planets and the lowest-mass [[star]]s. The 13-Jupiter-mass ({{Jupiter mass}}) cutoff is a rule of thumb rather than something of precise physical significance. Larger objects will burn most of their deuterium and smaller ones will burn only a little, and the {{jupiter mass|link=yes|13}} value is somewhere in between.<ref name="bodenheimer2013"/> The amount of deuterium burnt depends not only on the mass but also on the composition of the planet, especially on the amount of [[helium]] and deuterium present.<ref name="spiegel2011"/> The [[Extrasolar Planets Encyclopaedia]] includes objects up to {{Jupiter mass|60}}, and the [[Exoplanet Data Explorer]] up to {{Jupiter mass|24}}.<ref name="schneider2016"/><ref name="wright2010"/>

==Description==
[[File:Gas Giant Interiors.jpg|thumb|400px|right|Cutaway illustrations of the interior of the giant planets. Jupiter is shown with a rocky [[Planetary core|core]] overlaid by a deep layer of [[metallic hydrogen]].]]
A giant planet is a massive [[planet]] and has a thick atmosphere of [[hydrogen]] and [[helium]]. They may have a condensed "core" of heavier elements, delivered during the formation process.<ref name="stevenson2022">{{Cite journal |last1=Stevenson |first1=David J. |last2=Bodenheimer |first2=Peter |last3=Lissauer |first3=Jack J. |last4=D'Angelo |first4=Gennaro |date=2022-04-01 |title=Mixing of Condensable Constituents with H–He during the Formation and Evolution of Jupiter |journal=The Planetary Science Journal |volume=3 |issue=4 |page=74 |doi=10.3847/PSJ/ac5c44 |arxiv=2202.09476 |doi-access=free |bibcode=2022PSJ.....3...74S |issn=2632-3338}}</ref> This core may be partially or completely dissolved and dispersed throughout the hydrogen/helium envelope.<ref name="wilson2012"/><ref name="stevenson2022"/> In "traditional" giant planets such as [[Jupiter]] and [[Saturn]] (the gas giants) hydrogen and helium make up most of the mass of the planet, whereas they only make up an outer envelope on [[Uranus]] and [[Neptune]], which are instead mostly composed of [[water]], [[ammonia]], and [[methane]] and therefore increasingly referred to as "[[ice giant]]s".

Extrasolar giant planets that orbit very close to their stars are the [[exoplanet]]s that are easiest to detect. These are called [[hot Jupiter]]s and [[hot Neptune]]s because they have very high surface temperatures. Hot Jupiters were, until the advent of space-borne telescopes, the most common form of exoplanet known, due to the relative ease of detecting them with ground-based instruments.

Giant planets are commonly said to lack solid surfaces, but it is more accurate to say that they lack surfaces altogether since the gases that form them simply become thinner and thinner with increasing distance from the planets' centers, eventually becoming indistinguishable from the interplanetary medium. Therefore, landing on a giant planet may or may not be possible, depending on the size and composition of its core.

==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.

===Mega-Earths===
{{Main|Mega-Earth}}
The term "mega-Earth" or "massive solid planet" was used to refer to massive terrestrial exoplanets exceeding {{earth mass|10}}. With a mainly rocky composition, such a planet would have a density considerably greater than that of Earth and gas giants. [[Kepler-10c]] was traditionally classified as a mega-Earth, but was later found to be likely a volatile-rich mini-Neptune.<ref>{{cite journal | arxiv=1707.06192 | doi=10.1093/mnrasl/slx116 | doi-access=free | title=Pinning down the mass of Kepler-10c: The importance of sampling and model comparison | date=2017 | last1=Rajpaul | first1=V. | last2=Buchhave | first2=L. A. | last3=Aigrain | first3=S. | journal=Monthly Notices of the Royal Astronomical Society: Letters | volume=471 | pages=L125–L130 }}</ref><ref name="upping">[https://astrobites.org/2017/08/07/the-mass-of-kepler-10c-revisited-upping-the-radial-velocities-game/ The mass of Kepler-10c revisited: upping the radial velocities game], Leonardo dos Santos, 7 August 2017, Astrobites</ref> A sub-category known as "supermassive terrestrial planets" (SMTP) was used to refer to mega-Earths more than {{earth mass|30}}, such as [[Kepler-145b]].<ref>{{cite journal | arxiv=1601.07608 | doi=10.3847/0004-637X/830/1/43 | doi-access=free | title=Discovery and Validation of a High-Density Sub-Neptune from the K2 Mission | date=2016 | last1=Espinoza | first1=Néstor | last2=Brahm | first2=Rafael | last3=Jordán | first3=Andrés | last4=Jenkins | first4=James S. | last5=Rojas | first5=Felipe | last6=Jofré | first6=Paula | last7=Mädler | first7=Thomas | last8=Rabus | first8=Markus | last9=Chanamé | first9=Julio | last10=Pantoja | first10=Blake | last11=Soto | first11=Maritza G. | last12=Morzinski | first12=Katie M. | last13=Males | first13=Jared R. | last14=Ward-Duong | first14=Kimberly | last15=Close | first15=Laird M. | journal=The Astrophysical Journal | volume=830 | issue=1 | page=43 | bibcode=2016ApJ...830...43E }}</ref> Several [[pulsar planet]]s, such as [[PSR J1719−1438 b]], were discovered with masses higher than Jupiter's but with smaller radii when compared to gas giants, and are expected hence to be mostly crystallized diamond and oxygen.<ref name=diamondplanet/> As such, they may be carbon-rich planet-sized remnant inner cores of former companion stars shredded during interaction with a pulsar.<ref name=diamondplanet>{{cite journal|journal=[[Australian Geographic]]|url=http://www.australiangeographic.com.au/journal/solid-diamond-planet-found.htm|title=Solid diamond planet found|date=26 August 2011|archive-url=https://web.archive.org/web/20111006181112/http://www.australiangeographic.com.au/journal/solid-diamond-planet-found.htm|archive-date=6 October 2011}}</ref> However, per definitions, they would be instead considered as very low-mass white dwarfs, rather than high-density [[carbon planet|diamond planets]].<ref>{{cite magazine|magazine=[[Time (magazine)|Time]]|url=http://www.time.com/time/health/article/0,8599,2090471,00.html|archive-url=https://web.archive.org/web/20110826125732/http://www.time.com/time/health/article/0,8599,2090471,00.html|archive-date=26 August 2011|title=Scientists Discover a Diamond as Big as a Planet|first=Michael|last=Lemonick|date=26 August 2011}}</ref> [[Chthonian planet]]s such as [[TOI-849 b]], rocky or metallic planetary cores of an evaporated gas giant or [[brown dwarf]], may have masses comparable to mega-Earths, well over {{earth mass|30}}.<ref name="hebrard">Hébrard, G.; {{ill|lt=Lecavelier Des Étangs, A.|Alain Lecavelier des Étangs|fr}}, Vidal-Madjar, A.; Désert, J.-M.; Ferlet, R. (2003), [https://arxiv.org/abs/astro-ph/0312384 ''Evaporation Rate of Hot Jupiters and Formation of chthonian Planets''], Extrasolar Planets: Today and Tomorrow, ASP Conference Proceedings, Vol. 321, held 30 June – 4 July 2003, [[Institut d'astrophysique de Paris]], France. Edited by Jean-Philippe Beaulieu, Alain Lecavelier des Étangs and Caroline Terquem.</ref><ref>{{cite journal | arxiv=1208.3499 | doi=10.1093/mnras/sts090 | doi-access=free | title=Transit timing observations from Kepler – VII. Confirmation of 27 planets in 13 multiplanet systems via transit timing variations and orbital stability | date=2013 | last1=Steffen | first1=Jason H. |author1-link=Jason H. Steffen | last2=Fabrycky | first2=Daniel C. | last3=Agol | first3=Eric |author3-link=Eric Agol | last4=Ford | first4=Eric B. | last5=Morehead | first5=Robert C. | last6=Cochran | first6=William D. | last7=Lissauer | first7=Jack J. |author7-link=Jack J. Lissauer| last8=Adams | first8=Elisabeth R. | last9=Borucki | first9=William J. |author9-link=William J. Borucki | last10=Bryson | first10=Steve | last11=Caldwell | first11=Douglas A. | last12=Dupree | first12=Andrea |author12-link=Andrea Dupree | last13=Jenkins | first13=Jon M. | last14=Robertson | first14=Paul | last15=Rowe | first15=Jason F. | last16=Seader | first16=Shawn | last17=Thompson | first17=Susan | last18=Twicken | first18=Joseph D. | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=428 | issue=2 | pages=1077–1087 }}</ref>

The possibility of massive solid planets up to {{Earth mass|thousands of}} forming around massive stars ([[B-type main-sequence star|B]] and [[O-type main-sequence star|O-type]] stars; {{val|5|–|120|u=solar mass}}) has also been suggested based on mass-radius relationships for rocky planets, proposing 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.<ref name="seager2007"/> However, a more recent research showed that the ratio of protoplanetary disk mass to stellar mass decreases rapidly for stars exceeding {{solar mass|10}}.<ref name=jonathan2011>{{cite journal|last1=Williams |first1=Jonathan P. |last2=Cieza |first2=Lucas A. |title=Protoplanetary Disks and Their Evolution |journal=Annual Review of Astronomy and Astrophysics |date=2011 |volume=49 |issue=1 |pages=67–117 |doi=10.1146/annurev-astro-081710-102548 |arxiv=1103.0556 |bibcode=2011ARA&A..49...67W }}</ref>

Per a model, one hypothesis suggested so-called [[blanet]]s, fundamentally similar to other planets, orbiting around a rotating [[supermassive black hole]] at least a million [[solar mass]]es ({{solar mass|link=y}}) may harbor masses comparable to that of massive solid planets. Although the runaway accretion of the gas onto blanets to become gas giants is possible, it is likely difficult. Nevertheless, this would also depend on how fast are the orbits of blanets filled with gas.<ref name="Wada2020">{{cite journal |last1= Wada|first1= K.|last2= Tsukamoto|first2= Y.|last3= Kokubo|first3= E.|title= Formation of "Blanets" from Dust Grains around the Supermassive Black Holes in Galaxies|journal= The Astrophysical Journal|year= 2021|volume= 909|issue= 1|page= 96|doi= 10.3847/1538-4357/abd40a|arxiv=2007.15198|bibcode= 2021ApJ...909...96W|s2cid= 220870610|doi-access= free}}</ref>

===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"/>

== Extrasolar giant planets ==
[[File:Plan79ceti.jpg|thumb|An artist's conception of [[79 Ceti b]], the first extrasolar giant planet found with a [[minimum mass]] less than Saturn.]]
{{See also|Hot Jupiter|Super-Jupiter|Sub-brown dwarf |Brown dwarf}}
Because of the limited [[Methods of detecting exoplanets|techniques currently available]] to detect [[exoplanet]]s, many of those found to date have been of a size associated, in the Solar System, with giant planets. Because these large planets are inferred to share more in common with Jupiter than with the other giant planets, some have claimed that "jovian planet" is a more accurate term for them. Many of the exoplanets are much closer to their parent stars and hence much hotter than the giant planets in the Solar System, making it possible that some of those planets are a type not observed in the Solar System. Considering the relative [[abundance of the chemical elements|abundances of the elements in the universe]] (approximately 98% hydrogen and helium) it would be surprising to find a predominantly rocky planet more massive than Jupiter. On the other hand, models of planetary-system formation have suggested that giant planets would be inhibited from forming as close to their stars as many of the extrasolar giant planets have been observed to orbit.

==Atmospheres==
The bands seen in the [[atmosphere of Jupiter]] are due to counter-circulating streams of material called zones and belts, encircling the planet parallel to its equator. The zones are the lighter bands, and are at higher altitudes in the atmosphere. They have an internal updraft and are high-pressure regions. The belts are the darker bands, are lower in the atmosphere, and have an internal downdraft. They are low-pressure regions. These structures are somewhat analogous to the high and low-pressure cells in Earth's atmosphere, but they have a very different structure—latitudinal bands that circle the entire planet, as opposed to small confined cells of pressure. This appears to be a result of the rapid rotation and underlying symmetry of the planet. There are no oceans or landmasses to cause local heating and the rotation speed is much higher than that of Earth.

There are smaller structures as well: spots of different sizes and colors. On Jupiter, the most noticeable of these features is the [[Great Red Spot]], which has been present for at least 300 years. These structures are huge storms. Some such spots are thunderheads as well.

== See also ==
{{cmn|
* [[Chthonian planet]]
* [[Planet Nine]]
* [[Planetary system]]
* [[Stellification]]
* [[Sudarsky's gas giant classification]]
* [[Terrestrial planet]]
* [[Tyche (hypothetical planet)]]
}}

==References==
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<ref name="d'angelo2011">{{cite book|last=D'Angelo|first=G.|author2=Durisen, R. H. |author3=Lissauer, J. J.|chapter=Giant Planet Formation |bibcode=2010exop.book..319D| title=Exoplanets |publisher=University of Arizona Press, Tucson, AZ| editor=S. Seager. |pages=319–346|date=2011|url=http://www.uapress.arizona.edu/Books/bid2263.htm|arxiv=1006.5486 }}</ref>

<ref name="spiegel2011">{{Cite journal|last1=Spiegel|first1=David S.|last2=Burrows|first2=Adam|last3=Milsom|first3=John A.|date=2011-01-20|title=The Deuterium-Burning Mass Limit for Brown Dwarfs and Giant Planets|journal=The Astrophysical Journal|volume=727|issue=1|page=57|doi=10.1088/0004-637X/727/1/57|arxiv=1008.5150 |bibcode=2011ApJ...727...57S |s2cid=118513110 |issn=0004-637X}}</ref>

<ref name="schneider2016">{{Cite book|last=Schneider|first=Jean|date=2016|title=Exoplanets versus brown dwarfs: the CoRoT view and the future|chapter=III.8 Exoplanets versus brown dwarfs: The CoRoT view and the future |page=157|doi=10.1051/978-2-7598-1876-1.c038|arxiv=1604.00917 |isbn=978-2-7598-1876-1 |s2cid=118434022 }}</ref>

<ref name="bodenheimer2013">{{cite journal|last=Bodenheimer|first=P.|author2=D'Angelo, G.|author3=Lissauer, J. J.|author4=Fortney, J. J.|author5=Saumon, D. |title=Deuterium Burning in Massive Giant Planets and Low-mass Brown Dwarfs Formed by Core-nucleated Accretion|journal=The Astrophysical Journal|date=2013|volume=770|issue=2|pages=120 (13 pp.)|doi=10.1088/0004-637X/770/2/120|arxiv = 1305.0980 |bibcode = 2013ApJ...770..120B |s2cid=118553341}}</ref>

<ref name="wright2010">{{cite journal| arxiv=1012.5676 |title=The Exoplanet Orbit Database|date=2010| bibcode = 2011PASP..123..412W |doi = 10.1086/659427| volume=123| issue=902|journal=Publications of the Astronomical Society of the Pacific| pages=412–422| last1=Wright|first1=J. T.| last2=Fakhouri|first2=O.|last3=Marcy|first3=G. W.| last4=Han| first4=E.| last5=Feng| first5=Y.| last6=Johnson| first6=John Asher| last7=Howard| first7=A. W.|  last8=Fischer|first8=D. A.|last9=Valenti |first9=J. A.| last10=Anderson| first10=J.| last11=Piskunov|first11=N.|s2cid=51769219}}</ref>

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<ref name="wilson2012">{{Cite journal|last1=Wilson|first1=Hugh F.|last2=Militzer|first2=Burkhard|date=2012-03-14|title=Rocky core solubility in Jupiter and giant exoplanets|journal=Physical Review Letters|volume=108|issue=11|article-number=111101|doi=10.1103/PhysRevLett.108.111101|pmid=22540454 |arxiv=1111.6309 |bibcode=2012PhRvL.108k1101W |s2cid=42226611 |issn=0031-9007}}</ref>

<ref name="mcfadden2007">{{cite book |author1=L. McFadden |author2=P. Weissman |author3=T. Johnson |title=Encyclopedia of the Solar System (2nd ed.) |publisher=[[Academic Press]] |date=2007 |isbn=978-0-12-088589-3 |url-access=registration |url=https://archive.org/details/encyclopediaofso0000unse_u6d1 }}</ref>

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<ref name="libby-roberts2020">{{Cite journal|last1=Libby-Roberts|first1=Jessica E.|last2=Berta-Thompson|first2=Zachory K.|last3=Desert|first3=Jean-Michel|last4=Masuda|first4=Kento|last5=Morley|first5=Caroline V.|last6=Lopez|first6=Eric D.|last7=Deck|first7=Katherine M.|last8=Fabrycky|first8=Daniel|last9=Fortney|first9=Jonathan J.|last10=Line|first10=Michael R.|last11=Sanchis-Ojeda|first11=Roberto|last12=Winn|first12=Joshua N.|date=2020-01-20|title=The Featureless Transmission Spectra of Two Super-Puff Planets|journal=The Astronomical Journal|volume=159|issue=2|page=57|doi=10.3847/1538-3881/ab5d36|arxiv=1910.12988 |bibcode=2020AJ....159...57L |s2cid=204950000 |issn=1538-3881 |doi-access=free }}</ref>

<ref name="PT-June2008">{{cite web |last=Burgasser |first=Adam J. |title=Brown dwarfs: Failed stars, super Jupiters |url=http://astro.berkeley.edu/~gmarcy/astro160/papers/brown_dwarfs_failed_stars.pdf |date=June 2008 |work=[[Physics Today]] |access-date=11 January 2016 |archive-url=https://web.archive.org/web/20130508182012/http://astro.berkeley.edu/~gmarcy/astro160/papers/brown_dwarfs_failed_stars.pdf |archive-date=8 May 2013 }}</ref>
</references> <!-- end of reflist -->

==Bibliography==
* SPACE.com: Q&A: The IAU's Proposed Planet Definition, 16 August 2006, 2:00 AM ET
* BBC News: Q&A New planets proposal Wednesday, 16 August 2006, 13:36 GMT 14:36 UK

==External links==
{{Commons}}
* SPACE.com: [http://www.space.com/scienceastronomy/060816_planet_qanda.html Q&A: The IAU's Proposed Planet Definition] 16 August 2006 2:00 am ET
* BBC News: [https://news.bbc.co.uk/2/hi/science/nature/4798205.stm Q&A New planets proposal] Wednesday, 16 August 2006, 13:36 GMT 14:36 UK
* Gas Giants in Science Fiction: [http://www.sf-encyclopedia.com/entry/gas_giant]
* Episode "Giants" on [[The Science Channel]] TV show ''Planets''

{{Solar System}}
{{exoplanet}}
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{{DEFAULTSORT:Gas Giant}}
[[Category:Giant planets| ]]
[[Category:Types of planet]]
[[Category:Solar System]]