Which piece of spectral data is necessary to determine the spectral class of a star

Answer 1

The most crucial piece of spectral data required to determine the spectral class of a star is its spectrum, which is a record of the light emitted or absorbed by the star at different wavelengths across the electromagnetic spectrum. By examining the features and characteristics present in the spectrum, such as the intensity of different absorption or emission lines, astronomers can assign a spectral class to the star.