Editing Color temperature (section)

==Color temperature in astronomy==
[[File:A0V-blackbody SPD comparison.png|thumb|upright=1.4|Characteristic spectral power distribution of an A0V star (''T''<sub>eff</sub> = 9500&nbsp;K, cf. [[Vega]]) compared to black-body spectra. The 15,000&nbsp;K black-body spectrum (dashed line) matches the visible part of the stellar SPD much better than the black body of 9500&nbsp;K. All spectra are normalized to intersect at 555 nanometers.]]
In [[astronomy]], the color temperature is defined by the local slope of the SPD at a given wavelength, or, in practice, a wavelength range. Given, for example, the [[color magnitude]]s ''B'' and ''V'' which are calibrated to be equal for an [[A V star|A0V star]] (e.g. [[Vega]]), the stellar color temperature <math>T_C</math> is given by the temperature for which the color index <math>B-V</math> of a black-body radiator fits the stellar one. Besides the <math>B-V</math>, other color indices can be used as well. The color temperature (as well as the correlated color temperature defined above) may differ largely from the effective temperature given by the radiative flux of the stellar surface. For example, the color temperature of an A0V star is about 15000&nbsp;K compared to an effective temperature of about 9500&nbsp;K.<ref>{{cite book | last=Unsöld | first=Albrecht  |author2=Bodo Baschek | title = Der neue Kosmos | edition = 6 | publisher = Springer | location = Berlin, Heidelberg, New York | year = 1999 | isbn = 3-540-64165-3}}</ref>

For most applications in astronomy (e.g., to place a star on the [[Hertzsprung–Russell diagram|HR diagram]] or to determine the temperature of a model flux fitting an observed spectrum) the [[effective temperature]] is the quantity of interest. Various color-effective temperature relations exist in the literature. There relations also have smaller dependencies on other stellar parameters, such as the stellar metallicity and surface gravity<ref>{{cite journal |last1=Casagrande |first1=Luca |title=The GALAH survey: effective temperature calibration from the InfraRed Flux Method in the Gaia system |journal=MNRAS |year=2021 |volume=507 |issue=2 |pages=2684–2696 |doi=10.1093/mnras/stab2304 |doi-access=free |arxiv=2011.02517 |bibcode=2021MNRAS.507.2684C }}</ref>