Editing Brown dwarf (section)

== Planets around brown dwarfs ==
[[File:Artist’s impression of the disc of dust and gas around a brown dwarf.jpg|thumb|Artist's impression of a disc of dust and gas around a brown dwarf<ref>{{cite press release |first1=Luca |last1=Ricci |first2=Leonardo |last2=Testi |first3=Douglas |last3=Pierce-Price |first4=John |last4=Stoke |title=Even Brown Dwarfs May Grow Rocky Planets |url=http://www.eso.org/public/news/eso1248/ |access-date=3 December 2012 |publisher=European Southern Observatory |archive-url=https://web.archive.org/web/20121203042337/http://www.eso.org/public/news/eso1248/ |archive-date=3 December 2012 |url-status=dead }}</ref>]]
According to the IAU working definition (from August 2018) an exoplanet can orbit a brown dwarf. It requires a mass below 13 {{Jupiter mass}} and a mass ratio of ''M''/''M''<sub>central</sub><2/(25+√{621}), or roughly 1/25. This means that an object with a mass up to 3.2&nbsp;{{Jupiter mass}} around a brown dwarf with a mass of 80&nbsp;{{Jupiter mass}} is considered a planet. It also means that an object with a mass up to 0.52&nbsp;{{Jupiter mass}} around a brown dwarf with a mass of 13&nbsp;{{Jupiter mass}} is considered a planet.<ref>{{cite journal |last1=Lecavelier des Etangs |first1=A. |last2=Lissauer |first2=Jack J. |date=2022-06-01 |title=The IAU working definition of an exoplanet |url=https://ui.adsabs.harvard.edu/abs/2022NewAR..9401641L |journal=New Astronomy Reviews |volume=94 |pages=101641 |doi=10.1016/j.newar.2022.101641 |arxiv=2203.09520 |bibcode=2022NewAR..9401641L |s2cid=247065421 |issn=1387-6473}}</ref>

The [[super-Jupiter]] planetary-mass objects [[2M1207b]], [[2MASS J044144]] and Oph 98 B that are orbiting brown dwarfs at large orbital distances may have formed by [[cloud collapse]] rather than accretion and so may be [[sub-brown dwarf]]s rather than [[planet]]s, which is inferred from relatively large masses and large orbits. The first discovery of a low-mass companion orbiting a brown dwarf ([[ChaHα8]]) at a small orbital distance using the [[Doppler spectroscopy|radial velocity technique]] paved the way for the detection of planets around brown dwarfs on orbits of a few AU or smaller.<ref>{{cite journal |last1=Joergens |first1=Viki |last2=Müller |first2=André |title=16–20 MJup Radial Velocity Companion Orbiting the Brown Dwarf Candidate Cha Hα 8 |journal=The Astrophysical Journal |year=2007 |volume=666 |issue=2 |pages=L113–L116 |doi=10.1086/521825 |bibcode=2007ApJ...666L.113J |arxiv=0707.3744|s2cid=119140521 }}</ref><ref>{{cite journal |last1=Joergens |first1=Viki |last2=Müller |first2=André |last3=Reffert |first3=Sabine |title=Improved radial velocity orbit of the young binary brown dwarf candidate Cha Hα 8 |journal=Astronomy and Astrophysics |date=2010 |volume=521 |issue=A24 |pages=A24 |doi=10.1051/0004-6361/201014853 |bibcode=2010A&A...521A..24J |arxiv=1006.2383|s2cid=54989533 }}</ref> However, with a mass ratio between the companion and primary in [[ChaHα8]] of about 0.3, this system rather resembles a binary star. Then, in 2008, the first planetary-mass companion in a relatively small orbit ([[MOA-2007-BLG-192Lb]]) was discovered orbiting a brown dwarf.<ref name="bennett2008">{{cite journal |last1=Bennet |first1=David P. |first2=Ian A. |last2=Bond |first3=Andrzej |last3=Udalski |first4=Takahiro |last4=Sumi |first5=Fumio |last5=Abe |first6=Akihiko |last6=Fukui |first7=Kei |last7=Furusawa |first8=John B. |last8=Hearnshaw |first9=Sarah |last9=Holderness |first10=Yoshitaka |last10=Itow |first11=Koki |last11=Kamiya |first12=Aarno V. |last12=Korpela |first13=Pamela M. |last13=Kilmartin |first14=Wei |last14=Lin |first15=Cho Hong |last15=Ling |first16=Kimiaki |last16=Masuda |first17=Yutaka |last17=Matsubara |first18=Noriyuki |last18=Miyake |first19=Yasushi |last19=Muraki |first20=Maiko |last20=Nagaya |first21=Teppei |last21=Okumura |first22=Kouji |last22=Ohnishi |first23=Yvette C. |last23=Perrott |first24=Nicholas J. |last24=Rattenbury |first25=Takashi |last25=Sako |first26=Toshiharu |last26=Saito |first27=S. |last27=Sato |first28=Ljiljana |last28=Skuljan |first29=Denis J. |last29=Sullivan |first30=Winston L. |last30=Sweatman |first31=Paul J. |last31=Tristram |first32=Philip C. M. |last32=Yock |first33=Marcin |last33=Kubiak |first34=Michał K. |last34=Szymański |first35=Grzegorz |last35=Pietrzyński |first36=Igor |last36=Soszyński 
|first37=O. |last37=Szewczyk |first38=Łukasz |last38=Wyrzykowski |first39=Krzysztof |last39=Ulaczyk |first40=Virginie |last40=Batista |first41=Jean-Philippe |last41=Beaulieu |first42=Stéphane |last42=Brillant |first43=Arnaud |last43=Cassan |first44=Pascal |last44=Fouqué |first45=Pierre |last45=Kervella |first46=Daniel |last46=Kubas |first47=Jean-Baptiste |last47=Marquette |arxiv=0806.0025 |title=A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192 |journal=The Astrophysical Journal |date=30 May 2008 |volume=684 |issue=1 |pages=663–683 |doi=10.1086/589940 |bibcode=2008ApJ...684..663B |s2cid=14467194 }}</ref>
<!-- Then, in 2013, the first planetary-mass companion (OGLE-2012-BLG-0358L b) in a relatively small orbit was discovered orbiting a brown dwarf.<ref>{{cite magazine |url=http://www.technologyreview.com/view/517556/first-planet-discovered-orbiting-a-brown-dwarf/ |title=First Planet Discovered Orbiting a Brown Dwarf |magazine=MIT Technology Review |date=29 July 2013 |access-date=29 July 2013}}</ref>
In 2015, the first terrestrial-mass planet orbiting a brown dwarf was found, OGLE-2013-BLG-0723LBb.<ref>{{cite journal |arxiv=1507.02388 |last1=Burrows |first1=Adam |title=A Venus-Mass Planet Orbiting a Brown Dwarf: Missing Link between Planets and Moons |journal=The Astrophysical Journal |volume=812 |issue=1 |pages=47 |last2=Hubbard |first2=William B. |last3=Lunine |first3=Jonathan I. |last4=Liebert |first4=James |last5=Kozłowski |first5=S. |last6=Skowron |first6=J. |last7=Poleski |first7=R. |last8=Soszyński |first8=I. |last9=Pietrukowicz |first9=P. |last10=Mróz |first10=P. |last11=Szymański |first11=M. K. |last12=Wyrzykowski |first12=Ł. |last13=Ulaczyk |first13=K. |last14=Pietrzyński |first14=G. |last15=Shvartzvald |first15=Y. |last16=Maoz |first16=D. |last17=Kaspi |first17=S. |last18=Gaudi |first18=B. S. |last19=Hwang |first19=K.-H. |last20=Choi |first20 = J.-Y. |last21=Shin |first21=I.-G. |last22=Park |first22=H. |last23=Bozza |first23=V. |year=2015 |doi=10.1088/0004-637X/812/1/47 |bibcode=2015ApJ...812...47U }}</ref> -->

Planets around brown dwarfs are likely to be [[carbon planet]]s depleted of water.<ref>{{cite journal |arxiv=1311.1228 |last1=Burrows |first1=Adam |title=The Atomic and Molecular Content of Disks Around Very Low-mass Stars and Brown Dwarfs |journal=The Astrophysical Journal |volume=779 |issue=2 |pages=178 |last2=Hubbard |first2=William B. |last3=Lunine |first3=Jonathan I. |last4=Liebert |first4=James |year=2013 |doi=10.1088/0004-637X/779/2/178 |bibcode=2013ApJ...779..178P |s2cid=119001471 }}</ref>

A 2017 study, based upon observations with [[Spitzer Space Telescope|Spitzer]] estimates that 175 brown dwarfs need to be monitored in order to guarantee (95%) at least one detection of a below earth-sized planet via the transiting method.<ref>{{cite journal |last1=He |first1=Matthias Y. |last2=Triaud |first2=Amaury H. M. J. |last3=Gillon |first3=Michaël |date=January 2017 |title=First limits on the occurrence rate of short-period planets orbiting brown dwarfs |journal=Monthly Notices of the Royal Astronomical Society |volume=464 |issue=3 |pages=2687–2697 |arxiv=1609.05053 |bibcode=2017MNRAS.464.2687H |doi=10.1093/mnras/stw2391 |doi-access=free |s2cid=53692008 }}</ref> JWST could potentially detect smaller planets. The orbits of planets and moons in the [[Solar System|solar system]] often align with the orientation of the host star/planet they orbit. Assuming the orbit of a planet is aligned with the [[Rotation|rotational axis]] of a brown dwarf or [[Rogue planet|planetary-mass object]], the geometric transit probability of an object similar to [[Io (moon)|Io]] can be calculated with the formula cos(79.5°)/cos([[Orbital inclination|inclination]]).<ref name=":122">{{cite journal |last1=Limbach |first1=Mary Anne |last2=Vos |first2=Johanna M. |last3=Winn |first3=Joshua N. |last4=Heller |first4=René |last5=Mason |first5=Jeffrey C. |last6=Schneider |first6=Adam C. |last7=Dai |first7=Fei |date=2021-09-01 |title=On the Detection of Exomoons Transiting Isolated Planetary-mass Objects |journal=The Astrophysical Journal |volume=918 |issue=2 |pages=L25 |arxiv=2108.08323 |bibcode=2021ApJ...918L..25L |doi=10.3847/2041-8213/ac1e2d |issn=0004-637X |doi-access=free}}</ref> The inclination was estimated for several brown dwarfs and planetary-mass objects. [[SIMP J013656.5+093347|SIMP 0136]] for example has an estimated inclination of 80°±12.<ref>{{cite journal |last1=Vos |first1=Johanna M. |last2=Allers |first2=Katelyn N. |last3=Biller |first3=Beth A. |date=2017-06-01 |title=The Viewing Geometry of Brown Dwarfs Influences Their Observed Colors and Variability Amplitudes |journal=The Astrophysical Journal |volume=842 |issue=2 |pages=78 |arxiv=1705.06045 |bibcode=2017ApJ...842...78V |doi=10.3847/1538-4357/aa73cf |doi-access=free |issn=0004-637X}}</ref> Assuming the lower bound of i≥68° for SIMP 0136, this results in a transit probability of ≥48.6% for close-in planets. It is however not known how common close-in planets are around brown dwarfs and they might be more common for lower-mass objects, as disk sizes seem to decrease with mass.<ref name=":16" />

Strong evidence of a [[circumbinary planet]] in a polar orbit around [[2M1510]] was presented in 2025. The discovery was made with the [[Very Large Telescope]].<ref name="Baycroft2025">{{Cite journal |last1=Baycroft |first1=Thomas A. |last2=Sairam |first2=Lalitha |last3=Triaud |first3=Amaury H. M. J. |last4=Correia |first4=Alexandre C. M. |date=2025-04-16 |title=Evidence for a polar circumbinary exoplanet orbiting a pair of eclipsing brown dwarfs |journal=Science Advances |volume=11 |issue=16 |pages=eadu0627 |doi=10.1126/sciadv.adu0627|doi-access=free |pmid=40238865 |pmc=12002110 |arxiv=2504.12209 |bibcode=2025SciA...11..627B }}</ref><ref name="ESOpress2025">{{Cite web |title="Big surprise": astronomers find planet in perpendicular orbit around pair of stars |url=https://www.eso.org/public/news/eso2508/ |access-date=2025-04-16 |website=www.eso.org |language=en}}</ref>

=== Habitability ===

Habitability for hypothetical planets [[orbit]]ing brown dwarfs has been studied. Computer models suggesting conditions for these bodies to have [[habitable planet]]s are very stringent, the [[habitable zone]] being narrow, close (T dwarf 0.005&nbsp;au) and decreasing with time, due to the cooling of the brown dwarf (they fuse for at most 10 million years).    The orbits there would have to be of extremely low [[Eccentricity (mathematics)|eccentricity]] (on the order of {{val|e=−6}}) to avoid strong [[tidal force]]s that would trigger a [[runaway greenhouse effect]] on the planets, rendering them uninhabitable. There would also be no moons.<ref>
{{cite journal |bibcode=2013AsBio..13..279B |arxiv=1211.6467 |doi=10.1089/ast.2012.0867 |title=Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary |date=2011 |last1=Barnes |first1=Rory |last2=Heller |first2=René |journal=Astrobiology |volume=13 |issue=3 |pages=279–291 |pmid=23537137 |pmc=3612282}}</ref>