Editing Brown dwarf (section)

== Formation and evolution ==
[[File:M1701117 R-SII-Ha(1).png|thumb|The [[HH 1165]] jet launched by the brown dwarf [[Mayrit 1701117]] in the outer periphery of the [[sigma Orionis]] cluster]]The earliest stage of brown dwarf formation is called proto- or pre-brown dwarf. Proto-brown dwarfs are low-mass equivalents of [[Protostar|protostars]] (class 0/I objects). Additionally Very Low Luminosity Objects (VeLLOs) that have L<sub>int</sub> ≤0.1-0.2 {{Solar luminosity|link=true}} are often proto-brown dwarfs. They are found in nearby [[Star formation|star-forming]] clouds. Around 67 promising proto-brown dwarfs and 26 pre-brown dwarfs are known as of 2024.<ref>{{citation |last1=Palau |first1=Aina |title=Observations of pre- and proto-brown dwarfs in nearby clouds: paving the way to further constraining theories of brown dwarf formation |date=2024-10-01 |url=https://ui.adsabs.harvard.edu/abs/2024arXiv241007769P/abstract |access-date=2024-10-25 |arxiv=2410.07769 |last2=Huelamo |first2=Nuria |last3=Barrado |first3=David |last4=Dunham |first4=Michael M. |last5=Lee |first5=Chang Won|journal=New Astronomy Reviews |volume=99 |doi=10.1016/j.newar.2024.101711 |bibcode=2024NewAR..9901711P }}</ref> As of 2017 there is only one known proto-brown dwarf that is connected with a large [[Herbig–Haro object]]. This is the brown dwarf [[Mayrit 1701117]], which is surrounded by a pseudo-disk and a Keplerian disk.<ref>{{cite journal |last1=Riaz |first1=Basmah |last2=Machida |first2=Masahiro N. |last3=Stamatellos |first3=Dimitris |date=July 2019 |title=ALMA reveals a pseudo-disc in a proto-brown dwarf |journal=Monthly Notices of the Royal Astronomical Society |volume=486 |issue=3 |pages=4114–4129 |doi=10.1093/mnras/stz1032 |doi-access=free |arxiv=1904.06418 |bibcode=2019MNRAS.486.4114R |s2cid=119286540 |issn=0035-8711 }}</ref> Mayrit 1701117 launches the 0.7-light-year-long jet [[HH 1165]], mostly seen in ionized [[sulfur]].<ref>{{cite web |first1=Basmah |last1=Riaz |first2=Joan |last2=Najita |url=http://www.noao.edu/news/2017/pr1701.php |title=Punching Above Its Weight, a Brown Dwarf Launches a Parsec-Scale Jet |website=National Optical Astronomy Observatory |access-date=2020-02-18 |archive-date=2020-02-18 |archive-url=https://web.archive.org/web/20200218195420/https://www.noao.edu/news/2017/pr1701.php |url-status=dead }}</ref><ref name="Riaz 47">{{cite journal |last1=Riaz |first1=Basmah |last2=Briceño |first2=Cesar |last3=Whelan |first3=Emma T. |last4=Heathcote |first4=Stephen |date=July 2017 |title=First Large-scale Herbig-Haro Jet Driven by a Proto-brown Dwarf |journal=Astrophysical Journal |volume=844 |issue=1 |pages=47 |doi=10.3847/1538-4357/aa70e8 |arxiv=1705.01170 |bibcode=2017ApJ...844...47R |s2cid=119080074 |issn=0004-637X |doi-access=free }}</ref>

Brown dwarfs form similarly to stars and are surrounded by [[protoplanetary disk]]s,<ref name=":4">{{cite journal |last1=Apai |first1=Dániel |last2=Pascucci |first2=Ilaria |author2-link=Ilaria Pascucci |last3=Bouwman |first3=Jeroen |last4=Natta |first4=Antonella |last5=Henning |first5=Thomas |last6=Dullemond |first6=Cornelis P. |year=2005 |title=The Onset of Planet Formation in Brown Dwarf Disks |journal=Science |volume=310 |issue=5749 |pages=834–6 |arxiv=astro-ph/0511420 |bibcode=2005Sci...310..834A |doi=10.1126/science.1118042 |pmid=16239438 |s2cid=5181947}}</ref> such as [[Cha 110913−773444]]. [[Circumstellar disc|Disks]] around brown dwarfs have been found to have many of the same features as disks around stars; therefore, it is expected that there will be accretion-formed planets around brown dwarfs.<ref name=":4"/> Given the small mass of brown dwarf disks, most planets will be terrestrial planets rather than gas giants.<ref name="tidalplanets">{{cite journal |last1=Burrows |first1=Adam |last2=Hubbard |first2=William B. |last3=Lunine |first3=Jonathan I. |last4=Liebert |first4=James |year=2011 |title=Tidal evolution of planets around brown dwarfs |journal=Astronomy & Astrophysics |volume=535 |pages=A94 |arxiv=1109.2906 |bibcode=2011A&A...535A..94B |doi=10.1051/0004-6361/201117734 |s2cid=118532416 }}</ref> If a giant planet orbits a brown dwarf across our line of sight, then, because they have approximately the same diameter, this would give a large signal for [[Transit method|detection by transit]].<ref>[[David C. Jewitt|Jewitt, David C.]], [http://isites.harvard.edu/fs/docs/icb.topic541038.files/ay98_reading10.pdf Pan-STARRS Science Overview] {{Webarchive|url=https://web.archive.org/web/20151016070851/http://isites.harvard.edu/fs/docs/icb.topic541038.files/ay98_reading10.pdf |date=2015-10-16 }}</ref> The accretion zone for planets around a brown dwarf is very close to the brown dwarf itself, so tidal forces would have a strong effect.<ref name="tidalplanets"/>

[[File:Nearby_young_brown_dwarf_disk_WISEA_J120037.79-784508.3.png|thumb|left|275px|Artist's depiction of brown dwarf W1200-7845]]
In 2020, the closest brown dwarf with an associated primordial disk (class II disk)&mdash;[[WISEA J120037.79-784508.3]] (W1200-7845)&mdash;was discovered by the [[Disk Detective]] project when classification volunteers noted its infrared excess. It was vetted and analyzed by the science team who found that W1200-7845 had a 99.8% probability of being a member of the ε Chamaeleontis (ε Cha) young [[moving group]] [[stellar association|association]]. Its parallax (using Gaia DR2 data) puts it at a distance of 102 parsecs (or 333 lightyears) from Earth&mdash;which is within the local Solar neighborhood.<ref>{{cite web|url=https://blog.diskdetective.org/2020/08/12/our-new-paper-discovery-of-nearby-young-brown-dwarf-disk/|title=Our New Paper: Discovery of Nearby Young Brown Dwarf Disk!|last=Schutte|first=Maria|date=2020-08-12|website=DiskDetective.org|access-date=2023-09-23}}</ref><ref>{{cite journal |last1=Schutte |first1=Maria C. |last2=Lawson |first2=Kellen D. |last3=Wisniewski |first3=John P. |last4=Kuchner |first4=Marc J. |last5=Silverberg |first5=Steven M. |last6=Faherty |first6=Jacqueline K. |last7=Gagliuffi |first7=Daniella C. Bardalez |last8=Kiman |first8=Rocio |last9=Gagné |first9=Jonathan |last10=Meisner |first10=Aaron |last11=Schneider |first11=Adam C. |last12=Bans |first12=Alissa S. |last13=Debes |first13=John H. |last14=Kovacevic |first14=Natalie |last15=Bosch |first15=Milton K.D. |last16=Luca |first16=Hugo A. Durantini |last17=Holden |first17=Jonathan |last18=Hyogo |first18=Michiharu |date=2020-08-04 |title=Discovery of a Nearby Young Brown Dwarf Disk |journal=The Astrophysical Journal |volume=160 |issue=4 |pages=156 |doi=10.3847/1538-3881/abaccd |arxiv=2007.15735v2 |bibcode=2020AJ....160..156S |s2cid=220920317 |issn=1538-3881 |doi-access=free }}</ref>

[[File:Brown dwarf proplyds Orion Nebula.jpg|thumb|right|brown dwarf proplyds in the Orion Nebula with [[Hubble Space Telescope|Hubble]] and [[James Webb Space Telescope|JWST]].]]
A paper from 2021 studied [[circumstellar disc]]s around brown dwarfs in [[stellar association]]s that are a few million years old and 140 to 200 parsecs away. The researchers found that these disks are not massive enough to form planets in the future. There is evidence in these disks that might indicate that planet formation begins at earlier stages and that planets are already present in these disks. The evidence for disk evolution includes a decreasing disk mass over time, dust grain growth and dust settling.<ref name=":16">{{cite journal |last1=Rilinger |first1=Anneliese M. |last2=Espaillat |first2=Catherine C.|author2-link=Catherine Espaillat |date=2021-11-01 |title=Disk Masses and Dust Evolution of Protoplanetary Disks around Brown Dwarfs |journal=The Astrophysical Journal |volume=921 |issue=2 |pages=182 |doi=10.3847/1538-4357/ac09e5 |arxiv=2106.05247 |bibcode=2021ApJ...921..182R |s2cid=235377000 |issn=0004-637X |doi-access=free }}</ref> Two brown dwarf disks were also found in absorption and at least 4 disks are [[photoevaporation|photoevaporating]] from external UV-ratiation in the [[Orion Nebula]]. Such objects are also called [[proplyd|proplyds]]. [[Proplyd 181−247]], which is a brown dwarf or low-mass star, is surrounded by a disk with a radius of 30 astronomical units and the disk has a mass of 6.2±1.0 {{jupiter mass}}.<ref name="Luhman2024">{{cite journal |last1 = Luhman  |first1 = K. L. |first2=C |last2=Alves de Oliveira |first3=I. |last3=Baraffe |first4=G. |last4=Chabrier |first5=E. |last5=Manjavacas |first6=R. J. |last6=Parker |first7=P. |last7=Tremblin |author-link1 = Kevin Luhman |author-link3=Isabelle Baraffe |date = 13 Oct 2024 |title = JWST/NIRSpec Observations of Brown Dwarfs in the Orion Nebula Cluster |journal = The Astrophysical Journal |volume = 975 |issue = 2 |page = 162 |doi = 10.3847/1538-4357/ad7b19 |doi-access = free |arxiv = 2410.10000 |bibcode = 2024ApJ...975..162L }}</ref> Disks around brown dwarfs usually have a radius smaller than 40 [[astronomical unit]]s, but three disks in the more distant [[Taurus molecular cloud]] have a radius larger than 70 au and were resolved with [[Atacama Large Millimeter Array|ALMA]]. These larger disks are able to form rocky planets with a mass >1 {{Earth mass|link=true}}.<ref>{{cite journal |last1=Ricci |first1=L. |last2=Testi |first2=L. |last3=Natta |first3=A. |last4=Scholz |first4=A. |last5=de Gregorio-Monsalvo |first5=I. |last6=Isella |first6=A. |date=2014-08-01 |title=Brown Dwarf Disks with ALMA |url=https://ui.adsabs.harvard.edu/abs/2014ApJ...791...20R |journal=The Astrophysical Journal |volume=791 |issue=1 |pages=20 |doi=10.1088/0004-637X/791/1/20 |arxiv=1406.0635 |bibcode=2014ApJ...791...20R |hdl=10023/8607 |s2cid=13180928 |issn=0004-637X}}</ref> There are also brown dwarfs with disks in associations older than a few million years,<ref>{{cite journal |last1=Boucher |first1=Anne |last2=Lafrenière |first2=David |last3=Gagné |first3=Jonathan |last4=Malo |first4=Lison |last5=Faherty |first5=Jacqueline K. |last6=Doyon |first6=René |last7=Chen |first7=Christine H. |date=2016-11-01 |title=BANYAN. VIII. New Low-mass Stars and Brown Dwarfs with Candidate Circumstellar Disks |journal=The Astrophysical Journal |volume=832 |issue=1 |pages=50 |doi=10.3847/0004-637X/832/1/50 |arxiv=1608.08259 |bibcode=2016ApJ...832...50B |s2cid=119017727 |issn=0004-637X |doi-access=free }}</ref> which might be evidence that disks around brown dwarfs need more time to dissipate. Especially old disks (>20 Myrs) are sometimes called [[Peter Pan disk]]s. Currently [[2MASS J02265658-5327032]] is the only known brown dwarf that has a Peter Pan disk.<ref>{{cite journal |last1=Silverberg |first1=Steven M. |last2=Wisniewski |first2=John P. |last3=Kuchner |first3=Marc J. |last4=Lawson |first4=Kellen D. |last5=Bans |first5=Alissa S. |last6=Debes |first6=John H. |last7=Biggs |first7=Joseph R. |last8=Bosch |first8=Milton K. D. |last9=Doll |first9=Katharina |last10=Luca |first10=Hugo A. Durantini |last11=Enachioaie |first11=Alexandru |last12=Hamilton |first12=Joshua |last13=Holden |first13=Jonathan |last14=Hyogo |first14=Michiharu |date=2020-02-01 |title=Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars |journal=The Astrophysical Journal |volume=890 |issue=2 |pages=106 |doi=10.3847/1538-4357/ab68e6 |arxiv=2001.05030 |bibcode=2020ApJ...890..106S |s2cid=210718358 |issn=0004-637X |doi-access=free }}</ref>

The brown dwarf [[Cha 110913−773444]], located 500 light-years away in the constellation Chamaeleon, may be in the process of forming a miniature planetary system. Astronomers from [[Pennsylvania State University]] have detected what they believe to be a disk of gas and dust similar to the one hypothesized to have formed the Solar System. Cha 110913−773444 is the smallest brown dwarf found to date ({{Jupiter mass|8}}), and if it formed a planetary system, it would be the smallest-known object to have one.<ref>{{cite journal |last1=Luhman |first1=Kevin L. |last2=Adame |first2=Lucía |last3=d'Alessio |first3=Paola |last4=Calvet |first4=Nuria|author4-link=Nuria Calvet |last5=Hartmann |first5=Lee |last6=Megeath |first6=S. T. |last7=Fazio |first7=G. G. |year=2005 |title=Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk |journal=The Astrophysical Journal |volume=635 |issue=1 |pages=L93–L96 |arxiv=astro-ph/0511807 |bibcode=2005ApJ...635L..93L |doi=10.1086/498868 |s2cid=11685964 }}</ref>