Sub-brown dwarf

Sub-brown dwarfs are formed in the manner of stars, through the collapse of a gas cloud (perhaps with the help of photo-erosion) but there is no consensus amongst astronomers on whether the formation process should be taken into account when classifying an object as a planet.[https://web.archive.org/web/20010502150203/http://www.space.com/scienceastronomy/solarsystem/planet_confusion_001101-1.html What is a Planet? Debate Forces New Definition], by Robert Roy Britt, 2 November 2000 Free-floating sub-brown dwarfs can be observationally indistinguishable from rogue planets, which originally formed around a star and were ejected from orbit. Similarly, a sub-brown dwarf formed free-floating in a star cluster may be captured into orbit around a star, making distinguishing sub-brown dwarfs and large planets also difficult. A definition for the term "sub-brown dwarf" was put forward by the IAU Working Group on Extra-Solar Planets (WGESP), which defined it as a free-floating body found in young star clusters below the lower mass cut-off of brown dwarfs.IAU WGESP, [http://www.astro.iag.usp.br/~dinamica/WGEP.html 'Position Statement on the Definition of "Planet"'], 28 February 2003

The smallest mass of gas cloud that could collapse to form a sub-brown dwarf is about 1 Jupiter mass (M_J).{{citation|bibcode=2003IAUS..211..529B|title=Nomenclature: Brown Dwarfs, Gas Giant Planets, and ?|last1=Boss|first1=Alan P.|last2=Basri|first2=Gibor|last3=Kumar|first3=Shiv S.|last4=Liebert|first4=James|last5=Martín|first5=Eduardo L.|last6=Reipurth|first6=Bo|last7=Zinnecker|first7=Hans|volume=211|year=2003|pages=529|journal=Brown Dwarfs }} This is because to collapse by gravitational contraction requires radiating away energy as heat and this is limited by the opacity of the gas.{{citation|arxiv=0907.2243v1|doi= 10.1088/0004-637X/702/1/805|title=Substellar Objects in Nearby Young Clusters (Sonyc): The Bottom of the Initial Mass Function in Ngc 1333|year=2009|last1=Scholz|first1=Alexander|last2=Geers|first2=Vincent|last3=Jayawardhana|first3=Ray|last4=Fissel|first4=Laura|last5=Lee|first5=Eve|author5-link=Eve Lee|last6=Lafreniere|first6=David|last7=Tamura|first7=Motohide|journal=The Astrophysical Journal|volume=702|issue= 1|pages=805–822|bibcode = 2009ApJ...702..805S |s2cid= 5102383}} A 3 M_J candidate is described in a 2007 paper.{{citation|arxiv=0711.2510v1|

title=Dusty disks at the bottom of the IMF

| first1=Aleks |last1=Scholz|first2= Ray|last2= Jayawardhana|year=2007|doi=10.1086/526340|journal=The Astrophysical Journal|volume=672|issue = 1|pages=L49–L52|bibcode = 2008ApJ...672L..49S }}

There is no consensus whether these companions of stars should be considered sub-brown dwarfs or planets. Some authors agree these objects should be considered sub-brown dwarfs, since they likely formed on their own, like a "failed star".{{cite journal |last1=Rodriguez |first1=David R. |last2=Zuckerman |first2=B. |last3=Melis |first3=Carl |last4=Song |first4=Inseok |date=May 2011 |title=The Ultra Cool Brown Dwarf Companion of WD 0806-661B: Age, Mass, and Formation Mechanism |journal=The Astrophysical Journal Letters |volume=732 |issue=2 |pages=L29 |doi=10.1088/2041-8205/732/2/L29 |arxiv=1103.3544 |bibcode=2011ApJ...732L..29R}}

• 2MASS J0441+2301 Bb

Nonetheless, the IAU working definition of an exoplanet ignored formation mechanism as a criterion, and based on it these objects would be considered planets.

• WD 0806-661 B
• HD 106906 b
• ROXs 42Bb

At around 2022 the IAU working definition of an exoplanet excludes these objects as planets.{{Cite journal |last1=Etangs |first1=A. Lecavelier des |last2=Lissauer |first2=Jack J. |date=2022-03-17 |title=The IAU Working Definition of an Exoplanet |journal=New Astronomy Reviews |volume=94 |pages=101641 |arxiv=2203.09520 |doi=10.1016/j.newar.2022.101641|bibcode=2022NewAR..9401641L }} The only fitting label would be as sub-brown dwarfs, but they are more often referred as planetary mass objects. Other definitions, like from the NASA Exoplanet Archive{{Cite web |title=Exoplanet Criteria for Inclusion in the Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/docs/exoplanet_criteria.html |access-date=2025-01-19 |website=exoplanetarchive.ipac.caltech.edu}} would include these as exoplanets. There is no consensus whether these companions of brown dwarfs should be considered sub-brown dwarfs or planets.

{{Main|WISE J0336−0143}}

WISE J0336−0143B, orbits a brown dwarf or sub-brown dwarf. The primary has a mass of 8.5 to 18 {{Jupiter mass}} and secondary has a mass of 5-11.5 {{Jupiter mass}}. This object does not fit the IAU working definition of an exoplanet. This definition requires a mass ratio of about q<0.04, but the mass ratio of WISE J0336−0143AB is q=0.61±0.05.{{Cite journal |last1=Calissendorff |first1=Per |last2=De Furio |first2=Matthew |last3=Meyer |first3=Michael |last4=Albert |first4=Loïc |last5=Aganze |first5=Christian |last6=Ali-Dib |first6=Mohamad |last7=Bardalez Gagliuffi |first7=Daniella C. |last8=Baron |first8=Frederique |last9=Beichman |first9=Charles A. |last10=Burgasser |first10=Adam J. |last11=Cushing |first11=Michael C. |last12=Faherty |first12=Jacqueline Kelly |last13=Fontanive |first13=Clémence |last14=Gelino |first14=Christopher R. |last15=Gizis |first15=John E. |date=2023-04-01 |title=JWST/NIRCam Discovery of the First Y+Y Brown Dwarf Binary: WISE J033605.05-014350.4 |journal=The Astrophysical Journal |volume=947 |issue=2 |pages=L30 |doi=10.3847/2041-8213/acc86d |issn=0004-637X |doi-access=free|arxiv=2303.16923 |bibcode=2023ApJ...947L..30C }} It also does not fit the definition of a rogue planet, because it is gravitationally bound to a brown dwarf (or possibly sub-brown dwarf). It could be considered a planet according to alternative definitions, but according to the IAU it only fits the definition of sub-brown dwarf.

{{Main|2M1207b}}

2M1207b orbits around a young brown dwarf with a circumstellar disk and itself is likely surrounded by a circumstellar disk. The mass ratio is well above the upper limit of q=0.04 for exoplanets according to the IAU.{{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 |doi=10.3847/2041-8213/acd635 |issn=0004-637X |doi-access=free|arxiv=2305.18603 |bibcode=2023ApJ...949L..36L }}

Other examples of planetary-mass objects orbiting brown dwarfs and with M_B<13 {{Jupiter mass}} and q>0.04:

• CFHTWIR-Oph 98B, with M_B={{Val|11.6|0.4|0.8}} {{Jupiter mass}} and q={{Val|0.509|0.017|0.023}}{{Cite journal |last1=Fontanive |first1=Clémence |last2=Allers |first2=Katelyn N. |last3=Pantoja |first3=Blake |last4=Biller |first4=Beth |last5=Dubber |first5=Sophie |last6=Zhang |first6=Zhoujian |last7=Dupuy |first7=Trent |last8=Liu |first8=Michael C. |last9=Albert |first9=Loïc |date=2020-12-01 |title=A Wide Planetary-mass Companion to a Young Low-mass Brown Dwarf in Ophiuchus |journal=The Astrophysical Journal |volume=905 |issue=2 |pages=L14 |doi=10.3847/2041-8213/abcaf8 |issn=0004-637X |doi-access=free|arxiv=2011.08871 |bibcode=2020ApJ...905L..14F }}
• 2MASS J0249-0557ABc, with M_c={{Val|11.6|1.3|1.0}} {{Jupiter mass}} and $q=\{M\_\{c\}\; \backslash over\; M\_\{AB\}\}=0.13${{Cite journal |last1=Dupuy |first1=Trent J. |last2=Liu |first2=Michael C. |last3=Allers |first3=Katelyn N. |last4=Biller |first4=Beth A. |last5=Kratter |first5=Kaitlin M. |last6=Mann |first6=Andrew W. |last7=Shkolnik |first7=Evgenya L. |last8=Kraus |first8=Adam L. |last9=Best |first9=William M. J. |date=2018-08-01 |title=The Hawaii Infrared Parallax Program. III. 2MASS J0249-0557 c: A Wide Planetary-mass Companion to a Low-mass Binary in the β Pic Moving Group |journal=The Astronomical Journal |volume=156 |issue=2 |pages=57 |doi=10.3847/1538-3881/aacbc2 |issn=0004-6256|doi-access=free |arxiv=1807.05235 |bibcode=2018AJ....156...57D }}

Also called rogue planets:

• WISE 0855–0714 3–10 M_J about 7 light years away
• S Ori 52
• UGPS 0722-05 10–25 M_J 13 light years away
• Cha 110913-773444 5–15 M_J 163 light years away
• CFBDSIR 2149−0403 4–7 M_J 130 light years away
• OTS 44 11.5 M_J 550 light years away
• PSO J318.5−22 6–8 M_J about 80 light years away

{{wiktionary}}

• Brown dwarf
• Fusor (astronomy)
• Giant planet
• Hot Jupiter
• Red dwarf
• Rogue planet
• Substellar object
• List of planet types
• Lists of astronomical objects

{{reflist}}

{{Star}}

{{Exoplanet}}

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Category:Types of planet

Category:Planetary-mass objects

Category:Free-floating substellar objects