The speed of a star does not directly affect its light spectrum. The light spectrum of a star primarily depends on its temperature and chemical composition.
When we analyze the light emitted by a star, we observe a continuous spectrum with various characteristic features. The spectrum typically exhibits absorption lines, known as spectral lines, at specific wavelengths. These lines correspond to the absorption of light by elements and molecules present in the star's outer layers.
The temperature of a star determines the overall shape of its spectrum. Hotter stars emit more high-energy, shorter-wavelength light, which shifts the spectrum towards the blue end of the electromagnetic spectrum. Cooler stars emit more low-energy, longer-wavelength light, shifting the spectrum towards the red end.
The chemical composition of a star affects the specific absorption lines in its spectrum. Each element has a unique set of absorption lines associated with it. By studying these lines, astronomers can identify the elements present in a star and determine their relative abundance.
However, the motion of a star can cause a phenomenon called Doppler shift, which affects the observed wavelengths of its spectral lines. If a star is moving towards us, the wavelengths of its spectral lines will be compressed, resulting in a blue shift. Conversely, if a star is moving away from us, the wavelengths will be stretched, causing a red shift. This Doppler shift provides information about a star's radial velocity, which is its speed towards or away from an observer. But it does not directly alter the shape or features of the star's spectrum related to temperature and composition.