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 starSelf-luminous object held together by its own self-gravity. Often refers to those objects which generate energy from nuclear reactions occurring at their cores, but may also be applied to stellar remnants such as neutron stars..