Color Index

Parameter defining how a star’s brightness varies with color. It is defined by taking the difference in magnitude (which is related logarithmically to intensity) at different wavelengths. For example, the B-V color index is defined by taking the difference between the magnitudes in the blue and visual regions of the spectrum and the U-B color index is the analogous difference between the UV and blue regions of the spectrum. The color index is directly related to the temperature of the star.

Some or all content above used with permission from J. H. Wittke.