View source for 2M1207b

{{Short description|Planetary-mass object orbiting the brown dwarf 2M1207}}
{{Infobox planet
| name                     = 2M1207b
| symbol                   =
| image                    = Exoplanet Comparison 2M1207 b.png
| image_size               =
| image_alt                =
| caption                  = Size comparison of 2M1207b with Jupiter.
| background               =
| bgcolour                 =
| label_width              =
<!-- DISCOVERY           -->
| discoverer               = [[Gael Chauvin|Chauvin]] et al.
| discovery_site           = [[Paranal Observatory]], [[Chile]]
| discovered               = April 2004
| discovery_method         = Imaged
| discovery_ref            =
<!-- DESIGNATIONS        -->
| exosolar planets         =
| minorplanet              =
| extrasolarplanet         = 
| mpc_name                 =
| pronounced               = 
| named_after              =
| alt_names                =
| mp_category              =
| adjectives               =
<!-- ORBITAL             -->
| orbit_ref                =
| orbit_diagram            =
| epoch                    =
| uncertainty              =
| observation_arc          =
| earliest_precovery_date  =
| apsis                    = astron
| aphelion                 =
| perihelion               =
| semimajor                = {{convert|24|-|231|AU|km|abbr=on}}<ref name="Blunt2017" />
| mean_orbit_radius        =
| eccentricity             = {{val|0.02|-|0.98}}<ref name="Blunt2017" />
| period                   = {{val|633|-|20046}}<ref name="Blunt2017" /> [[year|y]]
| synodic_period           =
| avg_speed                =
| mean_anomaly             =
| mean_motion              =
| inclination              = {{val|13|-|150}}<ref name="Blunt2017" />
| angular_dist             =
| asc_node                 = {{val|7|-|174}}<ref name="Blunt2017" />
| long_periastron          =
| time_periastron          = {{val|2107.69|-|12883.36}}<ref name="Blunt2017" />
| arg_peri                 = {{val|4|-|176}}<ref name="Blunt2017" />
| semi-amplitude           =
| satellite_of             =
| satellites               =
| star                     = [[2M1207]]
| allsatellites            =
| tisserand                =
<!-- PHYS CHARS          -->
| physical_ref             =
| dimensions               =
| mean_diameter            =
| mean_radius              = 1.15 {{Jupiter radius}}<ref>{{Cite EPE|name=2M1207 A|id=6811|access-date=2024-03-24}}</ref>
| equatorial_radius        =
| polar_radius             =
| flattening               =
| circumference            =
| surface_area             =
| volume                   =
| mass                     = {{val|5.5|0.5}}<ref name="Luhman et al 2023" /> {{Jupiter mass|link=y}}
| density                  =
| surface_grav             =
| moment_of_inertia_factor =
| escape_velocity          =
| rotation                 =
| sidereal_day             =
| rot_velocity             =
| axial_tilt               =
| albedo                   =
| single_temperature       = 1200 K<ref name="Luhman et al 2023" />
| spectral_type            = mid-to-late L<ref name="Luhman et al 2023" />
| magnitude                =
| abs_magnitude            =
| angular_size             =
| family                   =
<!-- ATMOSPHERE          -->
| atmosphere_ref           = 
| atmosphere               =
| scale_height             =
| surface_pressure         =
| atmosphere_composition   = hydrogen, water, carbon monoxide, helium<ref name="Luhman et al 2023" /><ref name="Barman et al" />
<!-- NOTES               -->
| note                     =
}}
'''2M1207b''' is a [[planetary-mass object]] [[planetary orbit|orbiting]] the [[brown dwarf]] [[2M1207]], in the constellation [[Centaurus]], approximately 170 [[light-year]]s from Earth.<ref name="mamajek">{{Cite web |last=Mamajek |first=Eric |date=November 8, 2007 |title=The Distance to the 2M1207 System |url=http://www.cfa.harvard.edu/~emamajek/memo_2m1207.html |url-status=dead |archive-url=https://web.archive.org/web/20080124115127/http://www.cfa.harvard.edu/~emamajek/memo_2m1207.html |archive-date=2008-01-24 |access-date=June 15, 2008}}</ref> It is one of the first candidate [[exoplanet]]s to be directly observed (by [[infrared]] imaging). It was discovered in April 2004 by the [[Very Large Telescope]] (VLT) at the [[Paranal Observatory]] in [[Chile]] by a team from the [[European Southern Observatory]] led by Gaël Chauvin.<ref name="chauvin04">{{Cite journal |last1=Chauvin |first1=G. |last2=Lagrange |first2=A.-M. |last3=Dumas |first3=C. |last4=Zuckerman |first4=B. |last5=Mouillet |first5=D. |last6=Song |first6=I. |last7=Beuzit |first7=J.-L. |last8=Lowrance |first8=P. |date=2004 |title=A giant planet candidate near a young brown dwarf: Direct VLT/NACO observations using IR wavefront sensing |journal=Astronomy & Astrophysics |volume=425 |issue=2 |pages=L29–L32 |bibcode=2004A&A...425L..29C |doi=10.1051/0004-6361:200400056 |arxiv=astro-ph/0409323 |issn=0004-6361}}</ref>  It is believed to be from 5 to 6 times the [[mass]] of [[Jupiter]]<ref name="Luhman et al 2023" /> and may orbit 2M1207 at a distance roughly as far from the brown dwarf as [[Pluto]] is from the [[Sun]].<ref name="encyc">{{Cite web |title=Star: 2M1207 |url=http://exoplanet.eu/star.php?st=2M1207 |archive-url=https://web.archive.org/web/20111006004013/http://exoplanet.eu/star.php?st=2M1207 |archive-date=2011-10-06 |access-date=June 15, 2008 |website=Extrasolar Planets Encyclopaedia}}</ref>

The object is a very hot [[gas giant]]; the estimated surface [[temperature]] is roughly 1200 [[kelvin|K]] (930&nbsp;°C or 1700&nbsp;°F),<ref name="Luhman et al 2023" /> mostly due to gravitational contraction.<ref name="mohanty">{{Cite journal |last1=Mohanty |first1=Subhanjoy |last2=Jayawardhana |first2=Ray |last3=Huelamo |first3=Nuria |last4=Mamajek |first4=Eric |date=2007-03-10 |title=The Planetary Mass Companion 2MASS 1207−3932B: Temperature, Mass, and Evidence for an Edge-on Disk |journal=The Astrophysical Journal |volume=657 |issue=2 |pages=1064–1091 |bibcode=2007ApJ...657.1064M |doi=10.1086/510877 |arxiv=astro-ph/0610550 |issn=0004-637X}}</ref>  Its [[mass]] is well below the calculated limit for [[deuterium fusion]] in brown dwarfs, which is 13 [[Jupiter mass]]es.  The projected [[distance]] between 2M1207b and its primary is around 40 [[astronomical unit|AU]] (similar to the mean distance between [[Pluto]] and the [[Sun]]).<ref name="estsep">Estimated observed projected separation from observed angular separation and estimated distance.</ref> Its [[infrared]] spectrum indicates the presence of [[water]] molecules in its atmosphere.<ref name="esopr" /><ref name="Barman et al">{{Cite journal |last1=Barman |first1=Travis S. |last2=Macintosh |first2=Bruce |last3=Konopacky |first3=Quinn M. |last4=Marois |first4=Christian |date=2011-07-01 |title=The Young Planet-mass Object 2M1207b: A Cool, Cloudy, and Methane-poor Atmosphere |url=https://ui.adsabs.harvard.edu/abs/2011ApJ...735L..39B |journal=The Astrophysical Journal |volume=735 |issue=2 |pages=L39 |arxiv=1106.1201 |bibcode=2011ApJ...735L..39B |doi=10.1088/2041-8205/735/2/L39 |issn=0004-637X |s2cid=44225360}}</ref> The object is not a likely candidate to support [[life]], either on its surface or on any [[satellite]]s.

==Discovery and identification==
[[File:Primera foto planeta extrasolar ESO.jpg|thumb|left|200px|Infrared image of 2M1207 (blueish) and 2M1207b (reddish). The two objects are separated by less than one [[arc second]] in Earth's sky. Image taken using the [[European Southern Observatory|ESO]]'s 8.2m Yepun [[Very Large Telescope|VLT]].]]

2M1207b is around 100 times fainter in the sky than its companion.{{sfn| Mohanty | Jayawardhana | Huelamo | Mamajek | 2007 | loc=Bolometric luminosity, Table 1}} It was first spotted as a "faint reddish speck of light" in 2004 by the [[Very Large Telescope|VLT]]. After the initial observation, there was some question as to whether the objects might be merely an [[optical double]], but subsequent observations by the ''[[Hubble Space Telescope]]'' and the VLT have shown that the objects move together and are therefore presumably a [[binary system (astronomy)|binary system]].<ref name="esopr">{{Cite press release |title=Yes, it is the Image of an Exoplanet: Astronomers Confirm the First Image of a Planet Outside of Our Solar System |date=April 30, 2005 |publisher=[[European Southern Observatory]] |url=http://www.eso.org/public/news/eso0515/ |accessdate=July 10, 2010}}</ref>

An initial [[photometry (astronomy)|photometric]] estimate for the distance to 2M1207b was 70 [[parsec]]s.<ref name="mamajek" /> In December 2005, American astronomer [[Eric Mamajek]] reported a more accurate distance ({{value|53|6|u=parsecs}}) to 2M1207b using the [[moving-cluster method]].<ref>{{Cite journal |last=Mamajek |date=2005 |title=A Moving Cluster Distance to the Exoplanet 2M1207b in the TW Hydrae Association  |journal=The Astrophysical Journal |volume=634 |issue=2 |pages=1385–1394 |arxiv=astro-ph/0507416 |bibcode=2005ApJ...634.1385M |doi=10.1086/468181  |s2cid=17162407}}</ref>  Recent trigonometric [[parallax]] results have confirmed this moving-cluster distance, leading to a distance estimate of 52.75{{±|1.04|1.00}} parsecs or 172 ± 3 [[light years]].<ref name="mamajek" />

==Properties==
Estimates for the mass, size, and temperature of 2M1207b are still uncertain.  Although spectroscopic evidence is consistent with a mass of 8 ± 2 Jupiter masses and a surface temperature of 1600 ± 100 [[kelvin]]s, theoretical models for such an object predict a [[luminosity (astronomy)|luminosity]] 10 times greater than observed.  Because of this, lower estimates for the mass and temperature have been proposed.  Alternatively, 2M1207b might be dimmed by a surrounding disk of dust and gas.<ref name="mohanty" />  As an unlikely possibility, Mamajek and Michael Meyer have suggested that the planet is actually much smaller, but is radiating away heat generated by a recent collision.<ref>{{Cite journal |last1=Mamajek |first1=Eric E. |last2=Meyer |first2=Michael R. |date=2007-10-20 |title=An Improbable Solution to the Underluminosity of 2M1207B: A Hot Protoplanet Collision Afterglow |journal=The Astrophysical Journal |volume=668 |issue=2 |pages=L175–L178 |bibcode=2007ApJ...668L.175M |doi=10.1086/522957 |arxiv=0709.0456 |issn=0004-637X}}</ref><ref>{{Cite web |date=January 9, 2008 |title=Planet collision could explain alien world's heat |url=https://www.newscientist.com/article/dn13163-planet-collision-could-explain-alien-worlds-heat.html |url-status=live |archive-url=https://web.archive.org/web/20080110105806/http://space.newscientist.com/article/dn13163-planet-collision-could-explain-alien-worlds-heat.html |archive-date=10 January 2008 <!--DASHBot--> |access-date=2008-01-11 |website=New Scientist Space Website}}</ref>

[[James Webb Space Telescope|JWST]] observations of 2M1207B with [[NIRSpec]] did not detect any [[methane]] (CH<sub>4</sub>) and only weak [[carbon monoxide]] (CO) in the atmosphere of this object. The best-fit models show stronger methane and carbon monoxide bands than observed. A weaker methane band is a sign for [[Brown dwarf#Role of vertical mixing|nonequilibrium chemistry]] for young low-mass objects. The weakness of carbon monoxide could be attributed to other effects, such as temperature gradient or cloud thickness. The researchers used cloudless models that show some inconsistency with the temperature and absorption of methane and carbon monoxide, which might be resolved in the future with models that include [[Cloud|clouds]].<ref name="Luhman et al 2023">{{Cite journal |last1=Luhman |first1=K. L. |last2=Tremblin |first2=P. |last3=Birkmann |first3=S. M. |last4=Manjavacas |first4=E. |last5=Valenti |first5=J. |last6=Alves de Oliveira |first6=C. |last7=Beck |first7=T. L. |last8=Giardino |first8=G. |last9=Lützgendorf |first9=N. |last10=Rauscher |first10=B. J. |last11=Sirianni |first11=M. |date=2023-06-01 |title=JWST/NIRSpec Observations of the Planetary Mass Companion TWA 27B |journal=The Astrophysical Journal |volume=949 |issue=2 |pages=L36 |arxiv=2305.18603 |bibcode=2023ApJ...949L..36L |doi=10.3847/2041-8213/acd635 |issn=0004-637X |doi-access=free}}</ref>

The JWST observations were also able to detect emission of hydrogen ([[Hydrogen spectral series#Paschen series (Bohr series, n′ = 3)|Paschen]] transitions) and the [[Helium]] I triplet at 1.083 μm. This is a sign of active [[Accretion disk|accretion]] from a small [[Circumstellar disc|circumstellar disk]] or [[circumplanetary disk]].<ref name="Luhman et al 2023" /> For now this disk remains undetected, but it might be detected in future observations by JWST at longer wavelengths.<ref>{{Cite web |last=Cassese |first=Ben |date=2023-06-28 |title=Baby Brown Dwarf Might be Growing: JWST Observations of TWA 27B |url=https://aasnova.org/2023/06/28/baby-brown-dwarf-might-be-growing-jwst-observations-of-twa-27b/ |access-date=2023-08-15 |website=AAS Nova |language=en-US}}</ref>

== Status as an exoplanet ==
Although the mass of 2M1207b is less than that required for deuterium fusion to occur, some 13 times the mass of Jupiter, and the image of 2M1207b has been widely hailed as the first direct image of an exoplanet, it may be questioned whether 2M1207b is actually a planet. {{Asof|2018}}, the [[International Astronomical Union]]'s (IAU) official definition of an exoplanet requires that the mass ratio of the orbiting object to the central object be below the [[Lagrange point#Stability|L4/L5 instability]], which is given by the equation M/M<sub>central</sub> < 2/(25+{{math|{{radical|621}}}}) ≈ 1/25.<ref name="IAU-definition"/><ref name="LecavelierEtangs2022"/> The mass ratio of 2M1207b and 2M1207 is approximately 0.22, which exceeds the L4/L5 instability threshold and therefore means 2M1207b does not qualify as an exoplanet under the IAU's definition.

Some other [[definition of a planet|definitions of the term ''planet'']] require a planet to have formed in the same way as the planets in the [[Solar System]] did, by secondary accretion in a [[protoplanetary disk]].<ref name="Soter2006"/>  With such a definition, if 2M1207b formed by direct [[gravitational collapse]] of a gaseous [[nebula]], it would be a [[sub-brown dwarf]] rather than a planet.  A similar debate exists regarding the identity of [[GQ Lupi b]], also first imaged in 2004.<ref name="Spacecom-2005"/>  On the other hand, the discovery of marginal cases like [[Cha 110913-773444]]—a free-floating, planetary-mass object—raises the question of whether distinction by formation is a reliable dividing line between stars/brown dwarfs and planets.<ref name="NASA-2005"/>In 2006, the IAU's Working Group on Extrasolar Planets described 2M1207b as a "possible planetary-mass companion to a brown dwarf."<ref name="IAU-list"/>

==See also==
* [[Extrasolar moon]]
* [[HD 172555]]
* [[Rogue planet]]

==References==
{{reflist|refs=

<ref name="IAU-definition">{{cite web
|title=Official Working Definition of an Exoplanet
|url=https://www.iau.org/science/scientific_bodies/commissions/F2/info/documents/
|work=IAU position statement
|access-date=29 November 2020
}}</ref>

<ref name="LecavelierEtangs2022">{{Cite journal |last1=Lecavelier des Etangs |first1=A. |last2=Lissauer |first2=Jack J. |date=June 2022 |title=The IAU working definition of an exoplanet |url=https://linkinghub.elsevier.com/retrieve/pii/S138764732200001X |journal=New Astronomy Reviews |language=en |volume=94 |pages=101641 |doi=10.1016/j.newar.2022.101641|arxiv=2203.09520 |bibcode=2022NewAR..9401641L |s2cid=247065421 }}</ref>

<ref name="Soter2006">E.g., {{Cite journal |last=Soter |first=Steven |date=2006 |title=What Is a Planet? |journal=The Astronomical Journal |volume=132 |issue=6 |pages=2513–2519 |bibcode=2006AJ....132.2513S |doi=10.1086/508861 |arxiv=astro-ph/0608359 |s2cid=261212633 |issn=0004-6256}}</ref>

<ref name="Spacecom-2005">{{Cite web |last=Britt |first=Robert Roy |date=April 30, 2005 |title=Fresh Debate over First Photo of Extrasolar Planet |url=https://www.space.com/1023-fresh-debate-photo-extrasolar-planet.html |access-date=June 16, 2008 |website=Space.com}}</ref>

<ref name="NASA-2005">{{Cite web |last=Clavin |first=Whitney |date=November 29, 2005 |title=A Planet With Planets? Spitzer Finds Cosmic Oddball |url=http://www.nasa.gov/vision/universe/starsgalaxies/spitzerf-20051129.html |access-date=June 16, 2008 |website=NASA |archive-date=October 11, 2012 |archive-url=https://web.archive.org/web/20121011011111/http://www.nasa.gov/vision/universe/starsgalaxies/spitzerf-20051129.html |url-status=dead }}</ref>

<ref name="IAU-list">{{Cite web |date=August 28, 2006 |title=Lists of Extrasolar Planets |url=http://www.dtm.ciw.edu/boss/planets.html |archive-url=https://web.archive.org/web/20080619062439/http://www.dtm.ciw.edu/boss/planets.html |archive-date=2008-06-19 |access-date=June 15, 2008 |website=IAU Working Group on Extrasolar Planets}}</ref>

<ref name="Blunt2017">{{Cite journal |last1=Blunt |first1=Sarah |last2=Nielsen |first2=Eric L. |last3=De Rosa |first3=Robert J. |last4=Konopacky |first4=Quinn M. |last5=Ryan |first5=Dominic |last6=Wang |first6=Jason J. |last7=Pueyo |first7=Laurent |last8=Rameau |first8=Julien |last9=Marois |first9=Christian |last10=Marchis |first10=Franck |last11=MacIntosh |first11=Bruce |last12=Graham |first12=James R. |last13=Duchêne |first13=Gaspard |last14=Schneider |first14=Adam C. |display-authors=1 |year=2017 |title=Orbits for the Impatient: A Bayesian Rejection-sampling Method for Quickly Fitting the Orbits of Long-period Exoplanets |journal=The Astronomical Journal |volume=153 |issue=5 |at=229 |arxiv=1703.10653 |bibcode=2017AJ....153..229B |doi=10.3847/1538-3881/aa6930 |s2cid=119223138 |doi-access=free}}</ref>

}}

==External links==
{{Commons category}}
* [http://www.eso.org/public/news/eso0515/ ESO Press Release 12/05:Yes, it is the Image of an Exoplanet]
* [http://news.bbc.co.uk/2/hi/science/nature/4501323.stm  BBC: Planet 'seen' around distant sun]
* [http://space.com/scienceastronomy/aas_exoplanet_050110.html Space.com – Astronomers Confident: Planet Beyond Solar System Has Been Photographed]
* [http://www.space.com/scienceastronomy/planet_photo_040910.html Space.com article on the discovery]
* {{Cite web |last=Jean Schneider |date=2011 |title=Notes for Planet 2M1207 b |url=https://exoplanet.eu/catalog/2m1207_b--237/ |url-status=live |archive-url=https://web.archive.org/web/20111109002803/http://exoplanet.eu/planet.php?p1=2M1207&p2=b |archive-date=9 November 2011 |access-date=3 October 2011 |website=[[Extrasolar Planets Encyclopaedia]]}}
* [https://web.archive.org/web/20041013153848/http://www.sc.eso.org/~gchauvin/Gg222.pdf "A Giant Planet Candidate Near a Young Brown Dwarf" (PDF)] from the [[European Southern Observatory]].
* [http://www.space.com/scienceastronomy/050430_exoplanet_image.html Space.com: Fresh Debate over First Photo of Extrasolar Planet]
* [https://arxiv.org/abs/astro-ph/0507416 "A Moving Cluster Distance to the Exoplanet 2M1207 B in the TW Hydrae Association"]
* [http://adsabs.harvard.edu/abs/2007ApJ...657.1064M "The Planetary Mass Companion 2MASS 1207-3932B: Temperature, Mass, and Evidence for an Edge-on Disk"]
* [https://www.newscientist.com/article/dn13163-planet-collision-could-explain-alien-worlds-heat.html "Planet collision could explain alien world's heat"]

===Catalog views: Aladin Lite===
* [http://aladin.unistra.fr/AladinLite/?target=12%2007%2033.460-39%2032%2054.57&fov=0.07&survey=CDS%2FP%2FDSS2%2Fcolor DSS color]
* [http://aladin.unistra.fr/AladinLite/?target=12%2007%2033.460-39%2032%2054.57&fov=0.07&survey=CDS%2FP%2FDSS2%2FNIR DSS near IR]
* [http://aladin.unistra.fr/AladinLite/?target=12%2007%2033.460-39%2032%2054.57&fov=0.01&survey=CDS%2FP%2FHLA%2FSDSSr sDSS red (high res)]

{{Sky|12|07|33.47|-|39|32|54.0|172}}{{Centaurus}}
[[Category:2M1207|b]]
[[Category:Centaurus]]
[[Category:TW Hydrae association]]
[[Category:Giant planets]]
[[Category:Exoplanets discovered in 2004]]
[[Category:Exoplanets detected by direct imaging]]