The amount of radiation emitted by a star, along with its temperature, determines its spectral type. Spectral type is a classification system that categorizes stars based on their spectral characteristics, which include the distribution of radiation intensity at different wavelengths.
Stars emit a continuous spectrum of radiation, which is essentially a range of wavelengths or colors. However, the distribution of this radiation varies depending on the star's temperature.
The spectral types of stars are often designated using the Harvard spectral classification system, which uses letters ranging from O, B, A, F, G, K, M (from hottest to coolest) to classify stars. This classification system is based on the presence and intensity of specific spectral lines or features in the star's spectrum.
The amount of radiation emitted by a star, or its luminosity, is related to its temperature. Hotter stars emit more radiation across a broader range of wavelengths, including higher-energy and shorter-wavelength radiation (such as ultraviolet light) as well as lower-energy and longer-wavelength radiation (such as infrared light).
Therefore, the amount of radiation emitted by a star affects the overall shape of its spectrum. The presence and intensity of specific spectral lines or features, such as absorption or emission lines associated with certain elements, indicate the star's temperature, composition, and other properties. By examining the spectrum of a star and analyzing these features, astronomers can determine its spectral type, which provides valuable information about the star's characteristics and evolutionary stage.