Electromagnetic Spectrum:The complete range of electromagnetic radiation, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, each with different wavelengths and frequencies.
Spectral Line: A narrow absorption or emission feature in the spectrum of an object, corresponding to specific energy transitions of atoms or molecules.
Redshift:The shift of spectral lines towards longer, or redder, wavelengths due to the Doppler effect, indicating the object is moving away from the observer.