Editing Brown dwarf (section)

==== Spectral class L ====
{{main|L dwarf}}
[[Image:L-dwarf-nasa-hurt.png|thumb|Artist's concept 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 165]]B, the cool companion to the white dwarf [[GD 165]], had none of the hallmark TiO features of M dwarfs. The subsequent identification of many objects like GD 165B ultimately led to the definition of a new [[spectral class]], the '''L dwarfs''', defined in the red optical region of the spectrum not by metal-oxide absorption bands (TiO, VO), but by metal [[hydride]] emission bands ([[FeH]], [[CrH]], [[magnesium hydride|MgH]], [[calcium hydride|CaH]]) and prominent atomic lines of [[alkali metal]]s (Na, K, Rb, Cs). {{As of|2013}}, over 900 L&nbsp;dwarfs had 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]] (DENIS), and the [[Sloan Digital Sky Survey]] (SDSS). This spectral class also contains the coolest main-sequence stars (>&nbsp;80&nbsp;''M''<sub>J</sub>), which have spectral classes L2 to L6.<ref>{{cite journal |last1=Smart |first1=Richard L. |last2=Bucciarelli |first2=Beatrice |last3=Jones |first3=Hugh R. A. |last4=Marocco |first4=Federico |last5=Andrei |first5=Alexandre Humberto |last6=Goldman |first6=Bertrand |last7=Méndez |first7=René A. |last8=d'Avila |first8=Victor de A. |last9=Burningham |first9=Ben |last10=Camargo |first10=Julio Ignácio Bueno de |last11=Crosta |first11=Maria Teresa |first12=Mario |last12=Daprà |first13=James S. |last13=Jenkins |first14=Regis |last14=Lachaume |first15=Mario G. |last15=Lattanzi |first16=Jucira L. |last16=Penna |first17=David J. |last17=Pinfield |first18=Dario Nepomuceno |last18=da Silva Neto |first19=Alessandro |last19=Sozzetti |first20=Alberto |last20=Vecchiato |date=December 2018 |title=Parallaxes of Southern Extremely Cool objects III: 118 L and T dwarfs |journal=MNRAS |volume=481 |issue=3 |pages=3548–3562 |doi=10.1093/mnras/sty2520 |doi-access=free |arxiv=1811.00672 |bibcode=2018MNRAS.481.3548S |s2cid=119390019 |issn=0035-8711 }}</ref>