Editing Main sequence (section)

== Properties ==
The majority of stars on a typical HR diagram lie along the main-sequence curve. This line is pronounced because both the [[stellar classification|spectral type]] and the [[luminosity]] depends only on a star's mass, at least to [[order of approximation|zeroth-order approximation]], as long as it is fusing hydrogen at its core—and that is what almost all stars spend most of their "active" lives doing.<ref name=mss_atoe/>

The temperature of a star determines its [[spectral type]] via its effect on the physical properties of [[plasma (physics)|plasma]] in its [[photosphere]]. A star's energy emission as a function of wavelength is influenced by both its temperature and composition. A key indicator of this energy distribution is given by the [[color index]], {{nowrap|''B'' − ''V''}}, which measures the star's [[apparent magnitude|magnitude]] in blue (''B'') and green-yellow (''V'') light by means of filters.<ref group=note>By measuring the difference between these values, eliminates the need to correct the magnitudes for distance. However, this can be affected by [[Extinction (astronomy)|interstellar extinction]].</ref> This difference in magnitude provides a measure of a star's temperature.