Spectral index

Measure in astronomy

In astronomy, the spectral index of a source is a measure of the dependence of radiative flux density (that is, radiative flux per unit of frequency) on frequency. Given frequency, ν {\displaystyle \nu } , in Hz and radiative flux density, S ν {\displaystyle S_{\nu }} in Jy, the spectral index α {\displaystyle \alpha } is given implicitly by S ν ∝ ν α . {\displaystyle S_{\nu }\propto \nu ^{\alpha }.} If flux does not follow a power law in frequency, the spectral index itself is a function of frequency.

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