Editing Stellar classification (section)

===Class M===
{{See also|Red dwarf|Red giant|Red supergiant}}
[[File:M5V star spectrum.png|thumb|Spectrum of a hypothetical M5V star]]
Class&nbsp;M stars are by far the most common. About 76% of the main-sequence stars in the solar neighborhood are class&nbsp;M stars.<ref group="lower-alpha" name="proportions" /><ref group="lower-alpha">This rises to 78.6% if we include all stars. (See the above note.)</ref><ref name="LeDrew2001" /> However, class&nbsp;M main-sequence stars ([[red dwarf]]s) have such low luminosities that none are bright enough to be seen with the unaided eye, unless under exceptional conditions. The brightest-known M&nbsp;class main-sequence star is [[Lacaille 8760]], class&nbsp;M0V, with [[stellar magnitude|magnitude]]&nbsp;6.7 (the limiting magnitude for typical naked-eye visibility under good conditions being typically quoted as 6.5), and it is extremely unlikely that any brighter examples will be found.

Although most class&nbsp;M stars are red dwarfs, most of the largest-known supergiant stars in the Milky Way are class M stars, such as [[VY Canis Majoris]], [[VV Cephei]], [[Antares]], and [[Betelgeuse]]. Furthermore, some larger, hotter [[brown dwarf]]s are late class&nbsp;M, usually in the range of M6.5 to M9.5.

The spectrum of a class&nbsp;M star contains lines from [[oxide]] [[molecule]]s (in the [[visible spectrum]], especially [[Titanium(II) oxide|TiO]]) and all neutral metals, but absorption lines of hydrogen are usually absent. TiO bands can be strong in class&nbsp;M stars, usually dominating their visible spectrum by about M5. [[Vanadium(II) oxide]] bands become present by late&nbsp;M.

'''Example spectral standards:'''<ref name="Garrison"/>
* M3V – [[Gliese 581]]
* M0IIIa – [[Beta Andromedae]]
* M2III – [[Chi Pegasi]]
* M1-M2Ia-Iab – [[Betelgeuse]]
* M2Ia – [[Mu Cephei]] ("[[William Herschel|Herschel]]'s garnet")