Wien's displacement law: Difference between revisions

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== silent atmosphere ==
[[File:Brown Dwarf Binary CFBDSIR 1458+10.tif|thumb|Infrared image showing two brown dwarfs in the binary system [[CFBDSIR 1458+10]], obtained using the Laser Guide Star (LGS) [[Adaptive Optics]] system on the Keck II Telescope in Hawaii.]]
'''Brown dwarfs''' are [[substellar object]]s too low in mass to sustain [[hydrogen-1]] [[nuclear fusion|fusion]] reactions in their cores, unlike [[main sequence|main-sequence]] [[star]]s, which can. They occupy the mass range between the heaviest [[gas giant]]s and the lightest stars, with an upper limit around 75<ref>{{cite web|first = Alan|last = Boss|date = 2001-04-03|url = http://www.carnegieinstitution.org/News4-3,2001.html|title = Are They Planets or What?|publisher = Carnegie Institution of Washington|accessdate = 2006-06-08 |archiveurl = http://web.archive.org/web/20060928065124/http://www.carnegieinstitution.org/News4-3,2001.html <!-- Bot retrieved archive --> |archivedate = 2006-09-28}}</ref> to 80 [[Jupiter mass]]es (''M<sub>J</sub>''). Brown dwarfs heavier than about 13 ''M<sub>J</sub>'' are thought to [[deuterium burning|fuse deuterium]] and those above ~65 ''M<sub>J</sub>'', [[lithium burning|fuse lithium]] as well.<ref>{{cite web|url=http://www.universetoday.com/19237/dense-exoplanet-creates-classification-calamity/|title=Dense Exoplanet Creates Classification Calamity|author=Nicholos Wethington|publisher=''Universetoday.com''|date=October 6, 2008|accessdate=January 30, 2013}}</ref>


The difference between a very-low-mass brown dwarf and a [[gas giant|giant planet]] (~13 Jupiter masses) has been recently debated.<ref name=ab>{{cite web|url=http://astro.berkeley.edu/~gmarcy/astro160/papers/brown_dwarfs_failed_stars.pdf |title=A. J. Burgasser - Brown dwarfs: Failed stars, super Jupiters (2008) |format=PDF |date= |accessdate=2013-03-16}}</ref> One school of thought is based on formation; another, interior physics.<ref name=ab/>
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Dwarfs are categorized by spectral classification, with the major types being M, L, T, and Y.<ref name=ab/> Despite their name, brown dwarfs are different colours.<ref name=ab/> Many brown dwarfs would likely appear magenta to the human eye according to A. J. Burgasser,<ref name=ab>{{cite web|url=http://astro.berkeley.edu/~gmarcy/astro160/papers/brown_dwarfs_failed_stars.pdf |title=A. J. Burgasser - Brown dwarfs: Failed stars, super Jupiters (2008) |format=PDF |date= |accessdate=2013-03-16}}</ref> whereas another source has noted orange/red.<ref name=Cain>{{cite web|last=Cain|first=Fraser|title=If Brown Isn’t a Color, What Color are Brown Dwarfs?|url=http://www.universetoday.com/23247/if-brown-isnt-a-color-what-color-are-brown-dwarfs/|accessdate=24 September 2013|date=January 6, 2009}}</ref> The term brown dwarf was not chosen to indicate their colour.<ref name=ab/>
== Xiao Yan has not been golden and closed his eyes ==


Another debate is whether brown dwarfs should have experienced fusion at some point in their history. Some planets are known to orbit brown dwarfs: [[2M1207b]], [[MOA-2007-BLG-192Lb]], and [[2MASS J044144b]]. Brown dwarfs may have fully [[convective]] surfaces and interiors, with no chemical differentiation by depth.<ref>{{cite web|url=http://news.discovery.com/space/astronomy/violent-storms-rage-on-nearby-brown-dwarf-110913.htm|title=Violent Storms Rage on Nearby Brown Dwarf|author=Ian O'Neill|publisher=''Discovery.com''|date=Sep 13, 2011|accessdate=January 30, 3013}}</ref>
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At a distance of about 6.5 light years, the nearest known brown dwarf is [[Luhman 16]], a binary system of brown dwarfs discovered in 2013.
== at the moment is inevitably accelerated heart beat ==


==History==
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[[Image:Brown Dwarf Gliese 229B.jpg|thumb|250px|right|The smaller object is Gliese 229B, about 20 to 50 times the mass of Jupiter, orbiting the star [[Gliese 229]]. It is in the constellation [[Lepus (constellation)|Lepus]], about 19 light years from Earth.]]
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What became known as brown dwarfs were theorized to exist in the 1960s.<ref name=ab/>
 
 
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Brown dwarfs, a term coined by [[Jill Tarter]] in 1975,<ref name=Cain/><ref>Planet Quest: The Epic Discovery of Alien Solar Systems, Ken Croswell, Oxford University Press, 1999, ISBN 9780192880833, pages 118–119</ref> were originally called [[black dwarf]]s, a classification for dark substellar objects floating freely in space that were too low in mass to sustain hydrogen fusion. The term black dwarf currently refers to a [[white dwarf]] that has cooled to the point that it no longer emits significant light. Alternative names for brown dwarfs have been proposed, including [[Planetar (astronomy)|planetar]] and [[Substellar object|substar]].
 
 
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Early theories concerning the nature of the lowest-mass stars and the hydrogen-burning limit suggested that a [[Population I]] object with a mass less than 0.07 solar masses or a [[Population II]] object less than 0.09 solar masses would never go through normal [[stellar evolution]] and would become a completely [[degenerate star]] (Kumar 1963). The discovery of [[deuterium]]-burning down to 0.012 [[solar mass]]es and the impact of dust formation in the cool outer [[atmosphere]]s of brown dwarfs in the late 1980s brought these theories into question. However, such objects were hard to find because they emit almost no visible light. Their strongest emissions are in the [[infrared]] (IR) spectrum, and ground-based IR detectors were too imprecise at that time to readily identify any brown dwarfs.
 
 
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Since then, numerous searches by various methods have sought to find these objects. These methods included multi-color imaging surveys around field stars, imaging surveys for faint companions to [[main sequence|main-sequence]] dwarfs and [[white dwarfs]], surveys of young star clusters, and [[radial velocity]] monitoring for close companions.
 
 
</ul>
For many years, efforts to discover brown dwarfs were fruitless. In 1988, however, [[University of California, Los Angeles]] professors [[Eric Becklin]] and [[Benjamin Zuckerman|Ben Zuckerman]] identified a faint companion to a star known as GD 165 in an infrared search of white dwarfs. The spectrum of the companion GD 165B was very red and enigmatic, showing none of the features expected of a low-mass [[red dwarf]] star. It became clear that GD 165B would need to be classified as a much cooler object than the latest M dwarfs then known. GD 165B remained unique for almost a decade until the advent of the Two Micron All Sky Survey ([[2MASS]]) when [[J. Davy Kirkpatrick|Davy Kirkpatrick]], of the [[California Institute of Technology]], and others discovered many objects with similar colors and spectral features.
 
Today, GD 165B is recognized as the prototype of a class of objects now called "L dwarfs".{{citation needed|date=June 2013}} Although the discovery of the coolest dwarf was highly significant at the time, it was debated whether GD 165B would be classified as a brown dwarf or simply a very-low-mass star, because observationally it is very difficult to distinguish between the two.{{citation needed|date=June 2013}}
 
Soon after the discovery of GD 165B, other brown-dwarf candidates were reported. Most failed to live up to their candidacy, however, because the absence of lithium showed them to be stellar objects. True stars [[lithium burning|burn their lithium]] within a little over 100 [[Myr]], whereas brown dwarfs (which can, confusingly, have temperatures and luminosities similar to true stars) will not. In other words, the detection of lithium in the atmosphere of a candidate object ensures that, as long as it is older than the relatively young age of 100 Myr, it is a brown dwarf.
 
In 1995, the study of brown dwarfs changed substantially with the discovery of two incontrovertible substellar objects ([[Teide 1]] and [[Gliese 229B]]), which were identified by the presence of the 670.8&nbsp;nm lithium line. The most notable of these objects was the latter, which was found to have a temperature and luminosity well below the stellar range. Remarkably, its near-infrared spectrum clearly exhibited a methane absorption band at 2 micrometres, a feature that had previously only been observed in the atmospheres of giant planets and that of [[Saturn]]'s moon [[Titan (moon)|Titan]]. Methane absorption is not expected at the temperatures of main-sequence stars. This discovery helped to establish yet another spectral class even cooler than L dwarfs, known as "T dwarfs", for which Gliese 229B is the prototype.
 
The first confirmed brown dwarf was discovered by Spanish astrophysicists Rafael Rebolo (head of team), Maria Rosa Zapatero Osorio, and Eduardo Martín in 1994.<ref>{{cite web|url=http://www.iac.es/ |title=Instituto de Astrofísica de Canarias, IAC |publisher=Iac.es |date= |accessdate=2013-03-16}}</ref> They called this object [[Teide 1]] and it was found in the [[Pleiades]] open cluster. The discovery article was submitted to ''Nature'' in spring 1995, and published on September 14, 1995.<ref>{{cite web|url=http://www.nature.com/nature/journal/v377/n6545/abs/377129a0.html |title=Discovery of a brown dwarf in the Pleiades star cluster |publisher=Nature.com |date=1995-09-14 |accessdate=2013-03-16}}</ref> ''Nature'' highlighted "Brown dwarfs discovered, official" in the front page of that issue.
 
Teide 1 was discovered in images collected by the [[Instituto de Astrofísica de Canarias|IAC]] team on January 6, 1994 using the 80&nbsp;cm telescope (IAC 80) at [[Teide Observatory]] and its spectrum was first recorded in December 1994 using the 4.2 m William Herschel Telescope at [[Roque de los Muchachos Observatory]] (La Palma). The distance, chemical composition, and age of Teide 1 could be established because of its membership in the young Pleiades star cluster. Using the most advanced stellar and substellar evolution models at that moment, the team estimated for Teide 1 a mass 55 times the mass of [[Jupiter]],{{citation needed|date=June 2013}} which is clearly below the stellar-mass limit. The object became a reference in subsequent young brown dwarf related works.
 
In theory, a brown dwarf below 65 Jupiter masses is unable to burn lithium by thermonuclear fusion at any time during its evolution. This fact is one of the lithium test principles to examine the substellar nature in low-luminosity and low-surface-temperature astronomical bodies.
 
High-quality spectral data acquired by the Keck 1 telescope in November 1995 showed that Teide 1 had kept the initial lithium amount of the original molecular cloud from which Pleiades stars formed, proving the lack of thermonuclear fusion in its core. These observations confirmed that Teide 1 is a brown dwarf, as well as the efficiency of the spectroscopic lithium test.
 
For some time, Teide 1 was the smallest known object outside the Solar System that had been identified by direct observation. Since then, over 1,800 brown dwarfs have been identified,<ref name="DwarfArchives"/> even some very close to Earth like [[Epsilon Indi]] Ba and Bb, a pair of brown dwarfs gravitationally bound to a sunlike star around 12 light-years from the Sun, and [[Luhman 16]], a binary system of brown dwarfs about 6.5 light-years away.
 
==Theory==
{{star nav}}
The standard mechanism for [[stellar evolution|star birth]] is through the gravitational collapse of a cold interstellar cloud of gas and dust. As the cloud contracts it heats up from the release of gravitational [[potential energy]]. Early in the process the contracting gas quickly radiates away much of the energy, allowing the collapse to continue. Eventually, the central region becomes sufficiently dense to trap radiation. Consequently, the central temperature and density of the collapsed cloud increases dramatically with time, slowing the contraction, until the conditions are hot and dense enough for thermonuclear reactions to occur in the core of the [[protostar]]. For most stars, gas and radiation pressure generated by the [[thermonuclear fusion]] reactions within the core of the star will support it against any further gravitational contraction. [[Hydrostatic equilibrium]] is reached and the star will spend most of its lifetime fusing hydrogen into helium as a main-sequence star.
 
If, however, the mass of the protostar is less than about 0.08 solar mass, normal hydrogen [[thermonuclear fusion]] reactions will not ignite in the core. Gravitational contraction does not heat the small [[protostar]] very effectively, and before the temperature in the core can increase enough to trigger fusion, the density reaches the point where electrons become closely packed enough to create quantum [[electron degeneracy pressure]]. According to the brown dwarf interior models, typical conditions in the core for density, temperature and pressure are expected to be the following:
*<math>10\,\mathrm{g/cm^3} \,\lesssim\, \rho_c \,\lesssim\, 10^3\,\mathrm{{g}/{cm^{3}}} </math>
*<math>T_c \lesssim 3 \times 10^6\,\mathrm{K} </math>
*<math>P_c \sim 10^5\,\mathrm{Mbar}.</math>
<!-- [[File:tdwarf_art.jpg|thumb|left|alt=A picture of a Brown Dwarf|An artist's impression of a Brown Dwarf and its moon''.]] -->
This means that the protostar is not massive enough and not dense enough to ever reach the conditions needed to sustain hydrogen fusion. The infalling matter is prevented, by electron degeneracy pressure, from reaching the densities and pressures needed.
 
Further gravitational contraction is prevented and the result is a "failed star", or brown dwarf that simply cools off by radiating away its internal thermal energy.
 
===Distinguishing high-mass brown dwarfs from low-mass stars===
*[[Lithium]] is generally present in brown dwarfs and not in low-mass stars. Stars, which achieve the high temperature necessary for fusing hydrogen, rapidly deplete their lithium. This occurs by a collision of [[lithium-7]] and a [[proton]] producing two [[helium-4]] nuclei. The temperature necessary for this reaction is just below the temperature necessary for hydrogen fusion. Convection in low-mass stars ensures that lithium in the whole volume of the star is depleted. Therefore, the presence of the lithium [[spectral line|line]] in a candidate brown dwarf's spectrum is a strong indicator that it is indeed substellar. The use of lithium to distinguish candidate brown dwarfs from low-mass stars is commonly referred to as the '''lithium test''', and was pioneered by [[Rafael Rebolo]], [[Eduardo Martín]] and [[Antonio Magazzu]]. However, lithium is also seen in very young stars, which have not yet had enough time to burn it all. Heavier stars, like the Sun, can retain lithium in their outer atmospheres, which never get hot enough for lithium depletion, but those are distinguishable from brown dwarfs by their size. Contrariwise, brown dwarfs at the high end of their mass range can be hot enough to deplete their lithium when they are young. Dwarfs of mass greater than 65&nbsp;Jupiter masses can burn off their lithium by the time they are half a billion years old,<ref>
{{cite web |url = http://library.worldtracker.org/Science/Science%20Magazine/science%20magazine%201997-1998/root/data/Science%201997-1998/pdf/1997_v276_n5317/p5317_1350.pdf |title = Brown Dwarfs: A Possible Missing Link Between Stars and Planets |last = Kulkarni |first = S. R. |publisher = Science Magazine |date = 30 May 1997 |work = Vol. 276 |accessdate= 25 April 2013 }}</ref> thus this test is not perfect.
*Unlike stars, older brown dwarfs are sometimes cool enough that, over very long periods of time, their atmospheres can gather observable quantities of [[methane]]. Dwarfs confirmed in this fashion include [[Gliese 229B]].
*Main-sequence stars cool, but eventually reach a minimum [[bolometric luminosity]] that they can sustain through steady fusion. This varies from star to star, but is generally at least 0.01% that of the Sun.{{Citation needed|reason=as in talk page|date=April 2013}} Brown dwarfs cool and darken steadily over their lifetimes: sufficiently old brown dwarfs will be too faint to be detectable.
*[[Iron rain]] as part of atmospheric convection processes is possible only in brown dwarfs, and not in small stars. The spectroscopy research into iron rain is still ongoing—and not all brown dwarfs will always have this atmospheric anomaly.
 
===Distinguishing low-mass brown dwarfs from high-mass planets===
[[File:Brown Dwarf HD 29587 B.png|thumb|right|400px|An artistic concept of the brown dwarf around the star [[HD 29587]], a companion known as [[HD 29587 B]], and estimated to be about 55 Jupiter masses.]]
A remarkable property of brown dwarfs is that they are all roughly the same radius as Jupiter. At the high end of their mass range (60–90 Jupiter masses), the volume of a brown dwarf is governed primarily by [[degenerate matter|electron-degeneracy]] pressure,<ref>{{cite journal|title=Planetesimals to Brown Dwarfs: What is a Planet?|date=2006-08-20|pages=193–216|author1=Gibor Basri|volume=34|author2=Brown|doi=10.1146/annurev.earth.34.031405.125058|journal=Ann.Rev.Earth Planet.Sci. |arxiv=astro-ph/0608417|bibcode = 2006AREPS..34..193B }}</ref> as it is in white dwarfs; at the low end of the range (10 Jupiter masses), their volume is governed primarily by [[Coulomb barrier|Coulomb pressure]], as it is in planets. The net result is that the radii of brown dwarfs vary by only 10–15% over the range of possible masses. This can make distinguishing them from planets difficult.
 
In addition, many brown dwarfs undergo no fusion; those at the [[Sub-brown dwarf|low end of the mass range]] (under 13&nbsp;Jupiter masses) are never hot enough to [[deuterium burning|fuse even deuterium]], and even those at the high end of the mass range (over 60&nbsp;Jupiter masses) cool quickly enough that they no longer undergo fusion after a period of time on the order of 10&nbsp;million years. However, there are ways to distinguish brown dwarfs from planets:
 
X-ray and infrared spectra are telltale signs. Some brown dwarfs emit [[X-ray]]s; and all "warm" dwarfs continue to glow tellingly in the red and [[infrared]] spectra until they cool to planetlike temperatures (under 1000&nbsp;K).
 
[[Gas giant]]s have some of the characteristics of brown dwarfs. For example, [[Jupiter]] and [[Saturn]] are both made primarily of hydrogen and helium, like the Sun. Saturn is nearly as large as Jupiter, despite having only 30% the mass. Three of the giant planets in the Solar System (Jupiter, Saturn, and [[Neptune]]<!-- Uranus emits only barely more heat than it receives from the Sun, per source -->) emit much more heat than they receive from the Sun.<ref>[http://astronomy.nmsu.edu/tharriso/ast105/UranusandNeptune.html The Jovian Planets: Uranus, and Neptune]</ref> And all four giant planets have their own "planetary systems"—their moons. Brown dwarfs form independently, like stars, but lack sufficient mass to "ignite" as stars do. Like all stars, they can occur singly or in close proximity to other stars. Some orbit stars and can, like planets, have eccentric orbits.
 
Currently, the [[International Astronomical Union]] considers an object with a mass above the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13&nbsp;Jupiter masses for objects of solar metallicity) to be a brown dwarf, whereas an object under that mass (and orbiting a star or stellar remnant) is considered a planet.<ref>{{cite web|title=Working Group on Extrasolar Planets: Definition of a "Planet"|work=IAU position statement|date=2003-02-28 |url=http://www.dtm.ciw.edu/boss/definition.html|accessdate=2006-09-09}}</ref>
 
The 13&nbsp;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 13&nbsp;Jupiter mass value is somewhere in between. The amount of deuterium burnt also depends to some extent on the composition of the object, specifically on the amount of [[helium]] and [[deuterium]] present and on the fraction of heavier elements, which determines the atmospheric opacity and thus the radiative cooling rate.<ref name=Spiegel2011>{{cite journal |last=Spiegel |first=David S. |coauthors=Burrows, Adam; Milson, John A. |title=The Deuterium-Burning Mass Limit for Brown Dwarfs and Giant Planets |journal=The Astrophysical Journal |volume=727 |issue=1 |page=57 |year=2011 |doi=10.1088/0004-637X/727/1/57 |arxiv=1008.5150 |bibcode=2011ApJ...727...57S}}</ref>
 
The [[Extrasolar Planets Encyclopaedia]] includes objects up to 25&nbsp;Jupiter masses, and the [[Exoplanet Data Explorer]] up to 24&nbsp;Jupiter masses. Objects below 13&nbsp;Jupiter-mass are sometimes studied under the label "[[sub-brown dwarf]]".
 
==Observations==
 
===Classification of brown dwarfs===
 
====Spectral class M====
[[Image:late-M-dwarf-nasa-hurt.png|thumb|left|Artist's vision of a late-M dwarf]]
There are brown dwarfs with a spectral class of M6.5 or later. They are also called late-M dwarfs.
 
====Spectral class L====<!-- L dwarf redirects here -->
[[Image:L-dwarf-nasa-hurt.png|thumb|Artist's vision of an L-dwarf]]
 
The defining characteristic of [[spectral class]] M, the coolest type in the long-standing classical stellar sequence, is an optical spectrum dominated by absorption bands of [[titanium(II) oxide]] (TiO) and [[vanadium(II) oxide]] (VO) molecules. However, [[GD 165B]], the cool companion to the white dwarf [[GD 165]], had none of the hallmark TiO features of M dwarfs. The subsequent identification of many field counterparts to GD 165B ultimately led Kirkpatrick and others to the definition of a new [[spectral class]], the '''L dwarfs''', defined in the red optical region not by weakening metal-oxide bands (TiO, VO), but strong metal [[hydride]] bands ([[iron(I) hydride|FeH]], [[chromium hydride|CrH]], [[magnesium hydride|MgH]], [[calcium hydride|CaH]]) and prominent [[alkali metal]] lines (Na I, K I, Cs I, Rb I). {{As of|2013}}, over 900 L&nbsp;dwarfs have been identified,<ref name="DwarfArchives"/> most by wide-field surveys: the Two Micron All Sky Survey ([[2MASS]]), the Deep Near Infrared Survey of the Southern Sky ([[Deep Near Infrared Survey|DENIS]]), and the Sloan Digital Sky Survey ([[Sloan Digital Sky Survey|SDSS]]).
 
====Spectral class T====<!-- T dwarf redirects here -->
[[Image:T-dwarf-nasa-hurt.png|thumb|left|Artist's vision of a T-dwarf]]
As GD 165B is the prototype of the L dwarfs, [[Gliese 229]]B is the prototype of a second new spectral class, the '''T dwarfs'''. Whereas [[near-infrared]] (NIR) spectra of L dwarfs show strong absorption bands of H<sub>2</sub>O and [[carbon monoxide]] (CO), the NIR spectrum of Gliese 229B is dominated by absorption bands from [[methane]] (CH<sub>4</sub>), features that were only found in the giant planets of the Solar System and [[Titan (moon)|Titan]]. CH<sub>4</sub>, H<sub>2</sub>O, and molecular [[hydrogen]] (H<sub>2</sub>) collision-induced absorption (CIA) give Gliese 229B blue near-infrared colors. Its steeply sloped red optical spectrum also lacks the FeH and CrH bands that characterize L dwarfs and instead is influenced by exceptionally broad absorption features from the [[alkali]] metals [[sodium|Na]] and [[potassium|K]]. These differences led Kirkpatrick to propose the T spectral class for objects exhibiting H- and K-band CH<sub>4</sub> absorption. {{As of|2013}}, 355 T&nbsp;dwarfs are known.<ref name="DwarfArchives"/> NIR classification schemes for T dwarfs have recently been developed by Adam Burgasser and Tom Geballe. Theory suggests that L dwarfs are a mixture of very-low-mass stars and sub-stellar objects (brown dwarfs), whereas the T dwarf class is composed entirely of brown dwarfs. Because of the absorption of [[sodium]] and [[potassium]] in the green part of the spectrum of T dwarfs, the actual appearance of T dwarfs to human [[visual perception]] is estimated to be not brown, but the color of [[Magenta (color)#Magenta dye (1860)|magenta coal tar dye]].<ref name=burrows>Burrows et al. [http://arxiv.org/abs/astro-ph/0103383 The theory of brown dwarfs and extrasolar giant planets]. Reviews of Modern Physics 2001; 73: 719–65 {{doi|10.1103/RevModPhys.73.719}}</ref><ref>[http://spider.ipac.caltech.edu/staff/davy/2mass/science/comparison.html "An Artist's View of Brown Dwarf Types"] Dr. Robert Hurt of the Infrared Processing and Analysis Center</ref> T-class brown dwarfs, such as [[WISE 0316+4307]], have been detected over 100 light-years from the Sun.
 
====Spectral class Y====<!-- Y class dwarf redirects here -->
[[Image:WISE 1828+2650 Brown dwarf.jpg|thumb|Artist's vision of a Y-dwarf]]
There is some doubt as to what, if anything, should be included in the class '''Y dwarfs'''.<ref name="Ben Burningham 2008 pp. 320">Exploring the substellar temperature regime down to ~550K, Ben Burningham et al., ''Monthly Notices of the Royal Astronomical Society'' '''391''', #1 (November 2008), pp. 320–333, {{doi|10.1111/j.1365-2966.2008.13885.x}}, {{bibcode|2008MNRAS.391..320B}}; see the abstract.</ref><ref name=Luhman2011/> They are expected to be much cooler than T-dwarfs. They have been modelled,<ref>{{cite journal |author1=Deacon |author2=Hambly |doi=10.1111/j.1365-2966.2006.10795.x |journal=Monthly Notices of the Royal Astronomical Society |volume=371 |title=The {{Sic|possib|lity|nolink=y|expected\possibility}} of detection of Ultracool Dwarfs with the UKIRT Infrared Deep Sky Survey |issue=4 |pages=1722–1730 |year=2006 |arxiv=astro-ph/0607305 |bibcode=2006MNRAS.371.1722D}}</ref> though there is no well-defined spectral sequence yet with prototypes.
 
In 2009, the coolest known brown dwarfs had estimated effective temperatures between 500 and 600 [[kelvin|K]], and have been assigned the spectral class T9. Three examples are the brown dwarfs [[CFBDS J005910.90-011401.3]], [[ULAS J133553.45+113005.2]], and [[ULAS J003402.77−005206.7]].<ref name=four600k>The Physical Properties of Four ~600 K T Dwarfs, S. K. Leggett et al., ''The Astrophysical Journal'' '''695''', #2 (April 2009), pp. 1517–1526, {{doi|10.1088/0004-637X/695/2/1517}}, {{bibcode|2009ApJ...695.1517L}}.</ref> The spectra of these objects display absorption around 1.55 [[micrometer]]s.<ref name=four600k /> Delorme et al. have suggested that this feature is due to absorption from [[ammonia]] and that this should be taken as indicating the T–Y transition, making these objects of type Y0.<ref name=four600k /><ref name=tytrans>CFBDS J005910.90-011401.3: reaching the T–Y brown dwarf transition?, P. Delorme et al., ''Astronomy and Astrophysics'' '''482''', #3 (May 2008), pp. 961–971, {{doi|10.1051/0004-6361:20079317}}, {{bibcode|2008A&A...482..961D}}.</ref> However, the feature is difficult to distinguish from absorption by water and [[methane]],<ref name=four600k /> and other authors have stated that the assignment of class Y0 is premature.<ref name="Ben Burningham 2008 pp. 320"/>
 
In April 2010, two newly discovered ultracool [[sub-brown dwarf]]s ([[UGPS 0722-05]] and [[SDWFS 1433+35]]<ref>{{cite arXiv | author=P. Eisenhart et al. | title=Ultracool Field Brown Dwarf Candidates Selected at 4.5 microns | eprint=1004.1436 | class=astro-ph.SR | year=2010| last2= Griffith | first2=Roger L. | last3=Stern | first3=Daniel | last4= Wright | first4=Edward L. | last5= Ashby | first5=Matthew L. N. | last6=Brodwin | first6=Mark | last7= Brown | first7=Michael J. I. | last8= Bussmann | first8=R. S. | last9=Dey | first9=Arjun | last10= Ghez | first10=A. M. | last11=Glikman | first11=Eilat | last12= Gonzalez | first12=Anthony H. | last13= Davy Kirkpatrick | first13=J. | last14=Konopacky | first14=Quinn | last15=Mainzer | first15=Amy | last16=Vollbach | first16=David | last17= Wright | first17=Shelley A. }}</ref>) were proposed as prototypes for spectral class Y0.
 
In February 2011, Luhman et al. reported the discovery of a ~300 K, 7-Jupiter-mass 'brown-dwarf' companion to a nearby white dwarf.<ref name=Luhman2011>{{cite journal|last=Luhman|first=K. L.|coauthors=Burgasser, A. J., Bochanski, J. J.|title=DISCOVERY OF A CANDIDATE FOR THE COOLEST KNOWN BROWN DWARF|journal=The Astrophysical Journal Letters|date=20 March 2011|volume=730|issue=1|pages=L9|doi=10.1088/2041-8205/730/1/L9|bibcode=2011ApJ...730L...9L|bibcode = 2011ApJ...730L...9L |arxiv = 1102.5411 }}</ref> Though of 'planetary' mass, Rodriguez et al. suggest it is unlikely to have formed in the same manner as planets.<ref name=Rodriguez2011>{{cite journal|last=Rodriguez|first=David R.|coauthors=Zuckerman, B., Melis, Carl, Song, Inseok|title=THE ULTRA COOL BROWN DWARF COMPANION OF WD 0806-661B: AGE, MASS, AND FORMATION MECHANISM|journal=The Astrophysical Journal|date=10 May 2011|volume=732|issue=2|pages=L29|doi=10.1088/2041-8205/732/2/L29|url=http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1103.3544|accessdate=29 April 2011|bibcode = 2011ApJ...732L..29R |arxiv = 1103.3544 }}</ref>
 
Shortly after that, Liu et al. published an account of a "very cold" (~370 K) brown dwarf orbiting another very-low-mass brown dwarf and noted that "Given its low luminosity, atypical colors and cold temperature, CFBDS J1458+10B is a promising candidate for the hypothesized Y spectral class."<ref name="Liu et al. 2011">{{cite arXiv|last=Liu|first=Michael C.|coauthors=Philippe Delorme, Trent J. Dupuy, Brendan P. Bowler, Loic Albert, Etienne Artigau, Celine Reyle, Thierry Forveille, Xavier Delfosse|date=28 Feb 2011|title=CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System|eprint=1103.0014|class=astro-ph.SR}}</ref>
 
In August 2011, scientists using data from NASA's [[Wide-field Infrared Survey Explorer]] (WISE) discovered six "Y dwarfs"—star-like bodies with temperatures as cool as the human body.<ref name=Plait2011>{{cite journal|last=Plait|first=Phil|title=WISE finds coolest brown dwarfs ever seen!|journal=Discovery Magazine|date=24 August 2011|url=http://blogs.discovermagazine.com/badastronomy/2011/08/24/wise-finds-coolest-brown-dwarfs-ever-seen/#.UnGKkHDkudE }}</ref><ref name=NASA2011>{{cite web|title=WISE Finds Few Brown Dwarfs Close To Home|date=8 June 2012|url=http://www.nasa.gov/mission_pages/WISE/news/wise20120608.html}}</ref>
[[File:WISE2010-040-rotate180.jpg|thumb|right|[[WISEPC J045853.90+643451.9|WISE 0458+6434]] is the first ultra-cool brown dwarf (green dot) discovered by [[Wide-field Infrared Survey Explorer|WISE]]. The green and blue comes from infrared wavelengths mapped to visible colors.]]
WISE data has revealed hundreds of new brown dwarfs. Of these, fourteen are classified as cool Ys.<ref name="DwarfArchives"/> One of the Y dwarfs, called [[WISE 1828+2650]], was, as of August 2011, the record holder for the coldest brown dwarf – emitting no visible light at all, this type of object resembles free-floating planets more than stars. WISE 1828+2650 was initially estimated to have an atmospheric temperature cooler than 300 K<ref>{{cite news|last=Morse|first=Jon|title=Discovered: Stars as Cool as the Human Body|url=http://science.nasa.gov/science-news/science-at-nasa/2011/23aug_coldeststars/|accessdate=24 August 2011}}</ref>—for comparison the upper end of [[room temperature]] is 298 K (25 °C, 80 °F). Its temperature has since been revised and newer estimates put it in the range of 250 to 400 K (−23–127 °C, −10–260 °F).<ref name="Beichman2013">{{cite doi|10.1088.2F0004-637X.2F764.2F1.2F101}}</ref>
 
===Spectral and atmospheric properties of brown dwarfs===
The majority of flux emitted by L and T dwarfs is in the 1 to 2.5 micrometre near-infrared range. Low and decreasing temperatures through the late M-, L-, and T-dwarf sequence result in a rich near-infrared [[spectrum]] containing a wide variety of features, from relatively narrow lines of neutral atomic species to broad molecular bands, all of which have different dependencies on temperature, gravity, and [[metallicity]]. Furthermore, these low temperature conditions favor condensation out of the gas state and the formation of grains.
 
Typical atmospheres of known brown dwarfs range in temperature from 2200 down to 750 [[Kelvin|K]].<ref name=burrows/> Compared to stars, which warm themselves with steady internal fusion, brown dwarfs cool quickly over time; more massive dwarfs cool slower than less massive ones.
 
===Observational techniques===
[[File:Relative star sizes.svg|thumb|300px|right|Estimated relative size of the planet Jupiter and brown dwarfs [[Gliese 229B]] and [[Teide 1]]]]
 
[[Coronagraph]]s have recently been used to detect faint objects orbiting bright visible stars, including Gliese 229B.
 
Sensitive telescopes equipped with charge-coupled devices (CCDs) have been used to search distant star clusters for faint objects, including Teide 1.
 
Wide-field searches have identified individual faint objects, such as [[Kelu-1]] (30 ly away)
 
Brown dwarfs are often discovered in surveys to discover [[extrasolar planet]]s. [[Methods of detecting extrasolar planets]] work for brown dwarfs as well, although brown dwarfs are much easier to detect.
 
===Milestones===
* 1995: First brown dwarf verified. [[Teide 1]], an M8 object in the [[Pleiades]] [[star cluster|cluster]], is picked out with a CCD in the Spanish Observatory of Roque de los Muchachos of the [[Instituto de Astrofísica de Canarias]].
: First methane brown dwarf verified. Gliese 229B is discovered orbiting red dwarf [[Gliese 229]]A (20 ly away) using an [[adaptive optics]] coronagraph to sharpen images from the 60-inch (1.5&nbsp;m) reflecting telescope at [[Palomar Observatory]] on Southern California's [[Mt. Palomar]]; follow-up infrared spectroscopy made with their 200-inch (5&nbsp;m) [[Hale telescope]] shows an abundance of methane.
 
* 1998: First X-ray-emitting brown dwarf found. Cha Halpha 1, an M8 object in the [[Chamaeleon complex|Chamaeleon I]] dark cloud, is determined to be an X-ray source, similar to convective late-type stars.
* December 15, 1999: First X-ray flare detected from a brown dwarf. A team at the University of California monitoring LP 944-20 (60 Jupiter masses, 16 ly away) via the [[Chandra X-ray Observatory]], catches a 2-hour flare.
* 27 July 2000: First radio emission (in flare and quiescence) detected from a brown dwarf. A team of students at the [[Very Large Array]] reported their observations of LP 944-20 in the 15 March 2001 issue of the journal ''[[Nature (journal)|Nature]]''.
 
===Brown dwarf as an X-ray source===
[[Image:Lp94420 duo m.jpg|thumb|300px|[[Chandra X-ray Observatory|Chandra]] image of LP 944-20 before flare and during flare]]
 
X-ray flares detected from brown dwarfs since 1999 suggest changing [[magnetic field of celestial bodies|magnetic fields]] within them, similar to those in very-low-mass stars.
 
With no strong central nuclear energy source, the interior of a brown dwarf is in a rapid boiling, or convective state. When combined with the rapid rotation that most brown dwarfs exhibit, [[convection]] sets up conditions for the development of a strong, tangled [[magnetic field]] near the surface. The flare observed by [[Chandra X-ray Observatory|Chandra]] from LP 944-20 could have its origin in the turbulent magnetized hot material beneath the brown dwarf's surface. A sub-surface flare could conduct heat to the atmosphere, allowing electric currents to flow and produce an X-ray flare, like a stroke of [[lightning]]. The absence of X-rays from LP 944-20 during the non-flaring period is also a significant result. It sets the lowest observational limit on steady X-ray power produced by a brown dwarf star, and shows that coronas cease to exist as the surface temperature of a brown dwarf cools below about 2800K and becomes electrically neutral.
 
Using NASA's [[Chandra X-ray Observatory]], scientists have detected X-rays from a low-mass brown dwarf in a multiple star system.<ref name=Williams>{{cite web |date=April 14, 2003|title=X-rays from a Brown Dwarf's Corona |url=http://www.williams.edu/Astronomy/jay/chapter18_etu6.html}}</ref> This is the first time that a brown dwarf this close to its parent star(s) (Sun-like stars TWA 5A) has been resolved in X-rays.<ref name=Williams/> "Our Chandra data show that the X-rays originate from the brown dwarf's coronal plasma which is some 3 million degrees Celsius", said Yohko Tsuboi of [[Chuo University]] in Tokyo.<ref name=Williams/> "This brown dwarf is as bright as the Sun today in X-ray light, while it is fifty times less massive than the Sun", said Tsuboi.<ref name=Williams/> "This observation, thus, raises the possibility that even massive planets might emit X-rays by themselves during their youth!"<ref name=Williams/>
 
===Recent developments===
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 (8 Jupiter masses), and if it formed a planetary system, it would be the smallest known object to have one. Their findings were published in the December 10, 2005 issue of Astrophysical Journal Letters.<ref>{{cite web|url=http://iopscience.iop.org/1538-4357/635/1/L93/ |title=Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk, Luhman, et al., 2005 |publisher=Iopscience.iop.org |date= |accessdate=2013-03-16}}</ref>
 
Recent observations of known brown dwarf candidates have revealed a pattern of brightening and dimming of infrared emissions that suggests relatively cool, opaque cloud patterns obscuring a hot interior that is stirred by extreme winds. The weather on such bodies is thought to be extremely violent, comparable to but far exceeding Jupiter's famous storms.
 
On January 8, 2013 astronomers using NASA's [[Hubble space telescope|Hubble]] and [[Spitzer space telescope|Spitzer]] space telescopes probed the stormy atmosphere of a brown dwarf named [[2MASS J22282889-431026]], creating the most detailed "weather map" of a brown dwarf thus far. It shows wind-driven, planet-sized clouds. The new research is a stepping stone toward a better understanding not only brown dwarfs, but also of the atmospheres of planets beyond the Solar System.<ref>{{cite web|title=NASA Space Telescopes See Weather Patterns in Brown Dwarf|url=http://hubblesite.org/newscenter/archive/releases/star/brown-dwarf/2013/02/|work=Hubblesite|publisher=NASA|accessdate=8 January 2013}}</ref>
 
[[NASA]]'s [[Wide-field Infrared Survey Explorer|WISE]] mission has detected 200 new brown dwarfs.<ref name="space2012">{{cite web
  |date=12 June 2012
  |title=Brown Dwarfs, Runts of Stellar Litter, Rarer than Thought
  |publisher=Space.com
  |author=Ian O'Neill (Discovery News)
  |url=http://www.space.com/16112-brown-dwarf-stars-sun-rare.html
  |accessdate=2012-12-28}}</ref> There are actually fewer brown dwarfs in our cosmic neighborhood than previously thought. Rather than one star for every brown dwarf, there may be as many as six stars for every brown dwarf.<ref name="space2012"/>
 
==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 the disc of dust and gas around a brown dwarf.<ref>{{cite news|title=Even Brown Dwarfs May Grow Rocky Planets|url=http://www.eso.org/public/news/eso1248/|accessdate=3 December 2012|newspaper=ESO Press Release}}</ref>]]
The planetary-mass objects [[2M1207b]], [[GQ Lupi b]] and [[2MASS J044144]] that are orbiting brown-dwarfs 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. However, in 2013, the first low-mass companion (OGLE-2012-BLG-0358L b) in a relatively small orbit was discovered orbiting a brown dwarf.<ref>{{cite web|url=http://www.technologyreview.com/view/517556/first-planet-discovered-orbiting-a-brown-dwarf/|title=First Planet Discovered Orbiting a Brown Dwarf|publisher=MIT Technology Review|date=29 July 2013|accessdate=29 July 2013}}</ref>
 
[[circumstellar disk|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>[http://arxiv.org/pdf/astro-ph/0511420 The onset of planet formation in brown dwarf disks], Dániel Apai, Ilaria Pascucci, Jeroen Bouwman, Antonella Natta, Thomas Henning, Cornelis P. Dullemond</ref> Given the small mass of brown dwarf disks, most planets will be terrestrial planets rather than gas giants.<ref name=tidalplanets>[http://arxiv.org/abs/1109.2906 Tidal evolution of planets around brown dwarfs], E. Bolmont, S. N. Raymond, and J. Leconte, 2011</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>[http://isites.harvard.edu/fs/docs/icb.topic541038.files/ay98_reading10.pdf Pan-STARRS SCIENCE OVERVIEW], David C. Jewitt</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/>
 
==Superlative brown dwarfs==
{{Main|List of brown dwarfs}}
* [[WD 0137-349]] B: first confirmed brown dwarf to have survived the primary's [[red giant]] phase.<ref>{{cite journal|title=Survival of a brown dwarf after engulfment by a red giant star|doi=10.1038/nature04987|author=Maxted P. F. L.|year=2006|journal=Nature|volume=442|page=543|pmid=16885979|issue=7102|arxiv = astro-ph/0608054 |bibcode = 2006Natur.442..543M |author-separator=|displayauthors=1|last2=Napiwotzki|last3=Dobbie|last4=Burleigh}}</ref>
* In 1984, it was postulated by some astronomers that the Sun may be orbited by an undetected brown dwarf (sometimes referred to as [[Nemesis (hypothetical star)|Nemesis]]) that could interact with the [[Oort cloud]] just as [[List of nearest stars#Future and past|passing stars]] can. But this theory has fallen out of favor.<ref name="Morrison">{{cite web
  |date=August 2, 2011
  |title=Scientists today no longer think an object like Nemesis could exist
  |publisher=NASA Ask An Astrobiologist
  |author=David Morrison
  |authorlink=David Morrison (astrophysicist)
  |url=http://astrobiology2.arc.nasa.gov/ask-an-astrobiologist/question/?id=16790
  |accessdate=2011-10-22}}</ref>
 
{| class="wikitable" style="text-align:center;"
|+Table of Firsts
! colspan="6" style="text-align:left;"| Brown Dwarfs
|- style="background:#efefef;"
! Title
! Brown Dwarf Name
! Spectral Type
! RA/Dec
! Constellation
! Notes
|-
| First discovered
| [[Teide 1|Teide 1 (Pleiades Open Star Cluster)]]
| M8
| 3<sup>h</sup>47<sup>m</sup>18.0<sup>s</sup> +24°22'31"
| [[Taurus (constellation)|Taurus]]
| Imaged in 1989 and 1994
|-
| First imaged with coronography
| [[Gliese 229 B]]
| T6.5
| 06<sup>h</sup>10<sup>m</sup>34.62<sup>s</sup> −21°51'52.1"
| [[Lepus (constellation)|Lepus]]
| Discovered 1994
|-
| First with [[planemo]]
| [[2M1207|2MASSW J1207334-393254]]
| M8
| 12<sup>h</sup>07<sup>m</sup>33.47<sup>s</sup> −39°32'54.0"
| [[Centaurus]]
|
|-
| First with a planetary mass in orbit about it
| [[2M1207]]
|
|
|
| Planet discovered in 2004
|-
| First with a [[Protoplanetary disk|dust disk]]
|
|
|
|
|
|-
| First with [[bipolar outflow]]
|
|
|
|
|
|-
| First field type (solitary)
| [[Teide 1]]
| M8
| 3<sup>h</sup>47<sup>m</sup>18.0<sup>s</sup> +24°22'31"
| Taurus
| 1995
|-
| First as a companion to a normal star
| [[Gliese 229 B]]
| T6.5
| 06<sup>h</sup>10<sup>m</sup>34.62<sup>s</sup> −21°51'52.1"
| Lepus
| 1995
|-
| First spectroscopic binary brown dwarf
| [[PPL 15 A, B]] <ref>{{Cite journal|arxiv=astro-ph/9908015 |title=[astro-ph/9908015&#93; PPl 15: The First Brown Dwarf Spectroscopic Binary |publisher=Arxiv.org |date=1999-08-02 |last1=Basri |first1=Gibor |last2=Martin |first2=Eduardo |doi=10.1086/301079 |journal=The Astronomical Journal |volume=118 |issue=5 |pages=2460–2465 }}</ref>
| M6.5
|
| Taurus
| Basri and Martin 1999
|-
| First eclipsing binary brown dwarf
| [[2M0535-05]] <ref>{{cite web|url=http://www.nature.com/nature/journal/v440/n7082/edsumm/e060316-09.html |title=[Discovery of two young brown dwarfs in an eclipsing binary system |publisher=Nature |date=2006-03-16 |accessdate=2013-07-08}}</ref>
<ref>{{Cite journal|arxiv=0704.3106 |title=[astro-ph/0704.3106&#93; A Surprising Reversal of Temperatures in the Brown-Dwarf Eclipsing Binary 2MASS J05352184-0546085 |publisher=Arxiv.org |date=2007-04-24 |last1= Stassun |first1=Keivan G. |last2= Mathieu |first2=Robert D. |last3= Valenti |first3=Jeff A. |doi=10.1086/519231 |journal=The Astrophysical Journal |volume=664 |issue=2 |pages=1154–1166 }}</ref>
| M6.5
|
| Orion
| Stassun et al. 2006, 2007 (Distance ~450 pc)
|-
| First binary brown dwarf of T Type
| [[Epsilon Indi|Epsilon Indi Ba, Bb]] <ref>{{cite web|url=http://www.eso.org/outreach/press-rel/pr-2003/pr-01-03.html |title=eso0303 - Discovery of Nearest Known Brown Dwarf |publisher=ESO |date=2003-01-13 |accessdate=2013-03-16}}</ref>
| T1 + T6
|
| Indus
| Distance: 3.626pc
|-
| First trinary brown dwarf
| [[DENIS-P J020529.0-115925]] A/B/C
| L5, L8 and T0
| 02<sup>h</sup>05<sup>m</sup>29.40<sup>s</sup> −11°59'29.7"
| [[Cetus]]
| Delfosse et al. 1997, [http://xxx.lanl.gov/abs/astro-ph/0410226 mentions]
|-
| First halo brown dwarf
| [[2MASS J05325346+8246465]]
| [[Subdwarf star|sd]]L7
| 05<sup>h</sup>32<sup>m</sup>53.46<sup>s</sup> +82°46'46.5"
| [[Gemini (constellation)|Gemini]]
| Adam J. Burgasser, et al. 2003
|-
| First Late-M spectra
| [[Teide 1]]
| M8
| 3<sup>h</sup>47<sup>m</sup>18.0<sup>s</sup> +24°22'31"
| Taurus
| 1995
|-
| First L spectra
|
|
|
|
|
|-
| First T spectra
| [[Gliese 229 B]]
| T6.5
| 06<sup>h</sup>10<sup>m</sup>34.62<sup>s</sup> −21°51'52.1"
| Lepus
| 1995
|-
| Latest T spectrum
| [[ULAS J003402.77−005206.7|ULAS J0034-00]]
| T9<ref name="fr.arxiv.org">{{cite journal|author1=Ben Burningham|author2=Pinfield|author3=Leggett|author4=Tamura|author5=Lucas|author6=Homeier|author7=Day-Jones|author8=Jones|author9=Clarke|title=Exploring the substellar temperature regime down to ~550K|year=2008|doi=10.1111/j.1365-2966.2008.13885.x|journal=Monthly Notices of the Royal Astronomical Society|volume=391|pages=320–333|arxiv=0806.0067|bibcode=2008MNRAS.391..320B|last10=Ishii|first10=M.|last11=Kuzuhara|first11=M.|last12=Lodieu|first12=N.|last13=Zapatero Osorio|first13=M. R.|last14=Venemans|first14=B. P.|last15=Mortlock|first15=D. J.|last16=Barrado y Navascués|first16=D.|last17=Martin|first17=E. L.|last18=Magazzù|first18=A.}}</ref>
|
| Cetus
| 2007
|-
| First Y spectrum
| [[CFBDS J005910.90-011401.3|CFBDS0059]]&nbsp;– pending.<ref name="tytrans"/> This is also classified as a T9 dwarf, due to its close resemblance to other T dwarfs<ref name="fr.arxiv.org"/>
| ~Y0
|
|
| 2008
|-
| First X-ray-emitting
| [[Cha Halpha 1]]
| M8
|
| [[Chamaeleon]]
| 1998
|-
| First X-ray flare
| LP 944-20
| M9V
| 03<sup>h</sup>39<sup>m</sup>35.22<sup>s</sup> −35°25'44.1"
| [[Fornax (constellation)|Fornax]]
| 1999
|-
| First radio emission (in flare and quiescence)
| [[LP 944-20]]
| M9V
| 03<sup>h</sup>39<sup>m</sup>35.22<sup>s</sup> −35°25'44.1"
| Fornax
| 2000
|}
 
{{Expand list|date=August 2008}}
 
{| class="wikitable" style="text-align:center;"
|+ Table of Extremes
! colspan="6" style="text-align:left;"| Brown Dwarfs
|- style="background:#efefef;"
! Title
! Brown Dwarf Name
! Spectral Type
! RA/Dec
! Constellation
! Notes
|-
| Oldest
|
|
|
|
|
|-
| Youngest
|
|
|
|
|
|-
| Heaviest
|
|
|
|
|
|-
| Metal-rich
|
|
|
|
|
|-
| Metal-poor
| [[2MASS J05325346+8246465]]
| [[Subdwarf star|sd]]L7
| 05<sup>h</sup>32<sup>m</sup>53.46<sup>s</sup> +82°46'46.5"
| [[Gemini (constellation)|Gemini]]
| distance is ~10–30pc, metallicity is 0.1–0.01[[Metallicity|Z]]<sub>[[Sun|Sol]]</sub>
|-
| Lightest
|
|
|
|
|
|-
| Largest
|
|
|
|
|
|-
| Smallest
|
|
|
|
|
|-
| Farthest
|[[WISP 0307-7243]]<ref>{{cite news|title = Discovery of Three Distant, Cold Brown Dwarfs in the WFC3 Infrared Spectroscopic Parallels Survey |publisher = arxiv.org|date = 2012-04-27|url = http://arxiv.org/abs/1204.6320|accessdate = 2012-05-01}}</ref>
|T4.5
|03<sup>h</sup>07<sup>m</sup>45.12<sup>s</sup> −72°43'57.5"
|
|Distance: 400pc
|-
| Nearest
| [[Luhman 16]]
|
|
|
| Distance: ~6.5 ly
|-
 
| Brightest
| [[Teegarden's star]]
| M6.5
|
|
| jmag=8.4
|-
| Dimmest
| [[WISE 1828+2650]]
| Y2
|
|
| jmag=23
|-
| Hottest
|
|
|
|
|
|-
| Coolest
| [[WISE 1828+2650]]<ref name=NASA2011>{{cite web|url=http://science.nasa.gov/science-news/science-at-nasa/2011/23aug_coldeststars/ |title=Discovered: Stars as Cool as the Human Body - NASA Science |publisher=Science.nasa.gov |date=2011-08-24 |accessdate=2013-03-16}}</ref>
| Y2
|
|
| Temperature 300 [[Kelvin|K]]
|-
| Most dense
| [[COROT-3b]]<ref>{{cite web|url=http://www.esa.int/esaCP/SEM9E91YUFF_index_0.html |title=ESA Portal – Exoplanet hunt update |publisher=Esa.int |date= |accessdate=2013-03-16}}</ref>
|
|
|
| [[List of transiting extrasolar planets|Transiting]] brown dwarf [[COROT-3b]] has {{jupiter mass|link=yes|22}} with a diameter 1.01±0.07 times that of Jupiter. This makes it twice as dense as the metal platinum.
|-
| Least dense
|
|
|
|
|
|}
 
==See also==
{{Portal|Star}}
* [[Dark matter]]
* [[Extrasolar planet]]
* [[Brown-dwarf desert]]
* [[Blue dwarf (red-dwarf stage)]]
* Orange dwarf—[[K-type main-sequence star]]
* Yellow dwarf—[[G-type main-sequence star]]
 
==References==
{{reflist|30em
| refs =
 
<ref name="DwarfArchives">{{cite web
  |date=6 November 2012
  |title=DwarfArchives.org: Photometry, spectroscopy, and astrometry of M, L, and T dwarfs
  |publisher=caltech.edu
  |author=Davy Kirkpatrick
  |url=http://spider.ipac.caltech.edu/staff/davy/ARCHIVE/index.shtml
  |accessdate=2012-12-28|authorlink=J. Davy Kirkpatrick
  |author2= Adam Burgasser
  }} (M=536, L=918, T=355, Y=14)</ref>
 
}}
 
==External links==
{{Wiktionary}}
{{commons|Brown dwarf}}
*[http://hubblesite.org/newscenter/archive/releases/2013/02/image/a/ HubbleSite newscenter – Weather patterns on a brown dwarf]
 
===History===
* S. S. Kumar, ''Low-Luminosity Stars''. Gordon and Breach, London, 1969—an early overview paper on brown dwarfs
* [http://www.bartleby.com/65/br/browndwa.html The Columbia Encyclopedia]
 
===Details===
* [http://www.dwarfarchives.org A current list of L and T dwarfs]
* [http://astron.berkeley.edu/~stars/bdwarfs/structbd.html A geological definition of brown dwarfs], contrasted with stars and planets (via Berkeley)
* Neill Reid's pages at the [[Space Telescope Science Institute]]:
** [http://www-int.stsci.edu/~inr/ldwarf1.html On spectral analysis] of [[M dwarf]]s, [[L dwarf]]s, and [[T dwarf]]s
** [http://www-int.stsci.edu/~inr/ldwarf3.html Temperature and mass characteristics] of low-temperature dwarfs
* [http://www.spaceref.com/news/viewpr.html?pid=2192 First X-ray from brown dwarf observed], Spaceref.com, 2000
* [http://www.ucm.es/info/Astrof/recopilaciones/enanasmarrones.html Brown Dwarfs and ultracool dwarfs (late-M, L, T)]—[[D. Montes]], UCM
* [http://www.space.com/scienceastronomy/060703_mystery_monday.html Wild Weather: Iron Rain on Failed Stars]—scientists are investigating astonishing weather patterns on brown dwarfs, Space.com, 2006
* [http://www.nasa.gov/vision/universe/starsgalaxies/brown_dwarf_detectives.html NASA Brown dwarf detectives]—Detailed information in a simplified sense
* [http://www.darkstar1.co.uk/ds3.htm Brown Dwarfs]—Website with general information about brown dwarfs (has many detailed and colorful artist's impressions)
 
===Stars===
* [http://ssc.spitzer.caltech.edu/documents/compendium/cha_halpha1/ Cha Halpha 1] stats and history
* [http://astron.berkeley.edu/~stars/bdwarfs/observbd.html A census of observed brown dwarfs] (not all confirmed), ca 1998
* [http://www.spaceref.ca/news/viewpr.html?pid=12596 Epsilon Indi Ba and Bb], a pair of brown dwarfs 12 ly away
* [http://www.iop.org/EJ/article/1538-4357/635/1/L93/20043.html Luhman et al., Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk]
* [http://www.gemini.edu/index.php?option=content&task=view&id=232 Discovery Narrows the Gap Between Planets and Brown Dwarfs, 2007]
* [http://xxx.lanl.gov/abs/astro-ph/0607305 Y-Spectral class for Ultra-Cool Dwarfs, N.R.Deacon and N.C.Hambly, 2006]
 
{{Star}}
{{Exoplanet}}
 
{{DEFAULTSORT:Brown Dwarf}}
[[Category:Brown dwarfs| ]]
[[Category:Definition of planet]]
[[Category:Star types]]
[[Category:Stellar phenomena]]
[[Category:Substellar objects]]
[[Category:Types of planet]]
 
{{Link GA|de}}
{{Link FA|hu}}

Revision as of 13:36, 8 February 2014

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