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"smaller" can be understood as closer to zero. "Lower" might be less likely to be misunderstood; alternative might be "more negative" Tags: Mobile edit Mobile web edit Advanced mobile edit |
The denominator of the first expression was incorrectly shown as 0.92(B-V)+1.6(-). This was corrected to 0.92(B-V)+1.7 <ref>https://arxiv.org/pdf/1201.1809.pdf</ref> |
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In principle, the temperature of a star can be calculated directly from the B−V index, and there are several formulae to make this connection.<ref name=Sekiguchi>Sekiguchi M. and Fukugita (2000). "A STUDY OF THE B-V COLOR-TEMPERATURE RELATION". AJ (Astrophysical Journal) 120 (2000) 1072. http://iopscience.iop.org/1538-3881/120/2/1072.</ref> A good approximation can be obtained by considering stars as [[black body|black bodies]], using Ballesteros' formula<ref name=Ballesteros>Ballesteros, F. J. (2012). "New insights into black bodies". EPL 97 (2012) 34008. {{ArXiv|1201.1809}}.</ref> (also implemented in the PyAstronomy package for Python):<ref name=PyAstronomy>BallesterosBV_T API http://www.hs.uni-hamburg.de/DE/Ins/Per/Czesla/PyA/PyA/index.html.</ref>
:<math>T = 4600\,\mathrm{K} \left( \frac{1}{0.92\;B\text{-}\!V + 1.
Color indices of distant objects are usually affected by [[extinction (astronomy)|interstellar extinction]], that is, they are [[interstellar reddening|redder]] than those of closer stars. The amount of reddening is characterized by [[Interstellar reddening|color excess]], defined as the difference between the '''observed color index''' and the '''normal color index''' (or '''intrinsic color index'''), the hypothetical true color index of the star, unaffected by extinction.
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