Blueshift is the phenomenon where light or other electromagnetic radiation from an object moves towards shorter wavelengths. This typically indicates that the object emitting the light is moving closer to the observer.
redshift: Redshift is the phenomenon where light or other electromagnetic radiation from an object moves towards longer wavelengths, indicating that it is moving away from the observer.
Doppler Effect: The change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.
spectral line: A dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light at a specific wavelength by a substance.