Editing Subdwarf (section)

{{Short description|Star of luminosity class VI under the Yerkes spectral classification system}}
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A '''subdwarf''', sometimes denoted by "sd", is a star with [[luminosity class]]&nbsp;VI under the [[stellar classification#Yerkes spectral classification|Yerkes spectral classification]] system. They are defined as [[star]]s with [[luminosity]]&nbsp;1.5 to 2 [[Absolute magnitude|magnitudes]] lower than that of main-sequence stars of the same [[spectral type]]. On a [[Hertzsprung–Russell diagram]] subdwarfs appear to lie below the [[main sequence]].{{efn|name=no_mark_HR_note}}

The term "subdwarf" was coined by [[Gerard Kuiper]] in 1939, to refer to a series of stars with anomalous spectra that were previously labeled as "intermediate [[white dwarfs]]".<ref name=Croswell-1995/>{{rp|style=ama|p= 87}}

Since [[Gerard Kuiper|Kuiper]] coined the term, the subdwarf type has been extended to lower-mass stars than were known at the time. Astronomers have also discovered an entirely different group of blue-white subdwarfs, making two distinct categories:
* [[#cool_subdwarf_anchor|Cool subdwarfs]]
* [[#hot_subdwarf_anchor|Hot subdwarfs]]{{efn|
name=no_mark_HR_note|
[[#hot_subdwarf_anchor|Hot subdwarfs]] are as yet fairly rarely seen stars, and their place on the [[Hertzsprung–Russell diagram|HR diagram]] at present is usually unmarked. Their place would be a streak lower than the main sequence, under the label "sequence" on the HR diagram at the right.
}}